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	$114.31	10.663%	$126.4989	$126.50	$126.50	$126.50
Purchase #2	$171.92	10.551%	$190.0593	$190.06	$190.05	$190.10
Purchase #3	$229.27	13.133%	$259.38	$259.38	$259.40	$259.40
Purchase #4	$109.62	12.334%	$123.1405	$123.14	$123.15	$123.10
Purchase #5	$84.40	8.133%	$91.2643	$91.26	$91.25	$91.30
Purchase #6	$173.26	13.494%	$196.6397	$196.64	$196.65	$196.60
Purchase #7	$142.40	6.271%	$151.3299	$151.33	$151.35	$151.30
7 purchase totals =	$1,025.18		$1,138.3126	$1,138.31	$1,138.35	$1,138.30