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	$54.31	4.720%	$56.8734	$56.87	$56.85	$56.90
Purchase #2	$13.32	11.310%	$14.8265	$14.83	$14.85	$14.80
Purchase #3	$219.69	4.446%	$229.4574	$229.46	$229.45	$229.50
Purchase #4	$111.56	3.252%	$115.1879	$115.19	$115.20	$115.20
Purchase #5	$244.71	8.223%	$264.8325	$264.83	$264.85	$264.80
Purchase #6	$104.27	4.584%	$109.0497	$109.05	$109.05	$109.00
Purchase #7	$238.97	12.639%	$269.1734	$269.17	$269.15	$269.20
7 purchase totals =	$986.83		$1,059.4008	$1,059.40	$1,059.40	$1,059.40