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	$136.51	10.548%	$150.9091	$150.91	$150.90	$150.90
Purchase #2	$214.29	13.402%	$243.0091	$243.01	$243.00	$243.00
Purchase #3	$173.27	6.381%	$184.3264	$184.33	$184.35	$184.30
Purchase #4	$189.87	10.320%	$209.4646	$209.46	$209.45	$209.50
Purchase #5	$42.78	6.817%	$45.6963	$45.70	$45.70	$45.70
Purchase #6	$236.96	12.316%	$266.144	$266.14	$266.15	$266.10
Purchase #7	$185.64	7.804%	$200.1273	$200.13	$200.15	$200.10
7 purchase totals =	$1,179.32		$1,299.6768	$1,299.68	$1,299.70	$1,299.60