Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$115.65	13.614%	$131.3946	$131.39	$131.40	$131.40
Purchase #2	$131.55	11.335%	$146.4612	$146.46	$146.45	$146.50
Purchase #3	$94.41	6.296%	$100.3541	$100.35	$100.35	$100.40
Purchase #4	$187.86	9.813%	$206.2947	$206.29	$206.30	$206.30
Purchase #5	$233.54	5.419%	$246.1955	$246.20	$246.20	$246.20
Purchase #6	$116.56	13.485%	$132.2781	$132.28	$132.30	$132.30
Purchase #7	$201.36	10.821%	$223.1492	$223.15	$223.15	$223.10
7 purchase totals =	$1,080.93		$1,186.1274	$1,186.12	$1,186.15	$1,186.20