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	$107.76	3.781%	$111.8344	$111.83	$111.85	$111.80
Purchase #2	$69.29	8.565%	$75.2247	$75.22	$75.20	$75.20
Purchase #3	$198.44	12.438%	$223.122	$223.12	$223.10	$223.10
Purchase #4	$56.55	9.544%	$61.9471	$61.95	$61.95	$61.90
Purchase #5	$11.42	4.717%	$11.9587	$11.96	$11.95	$12.00
Purchase #6	$139.36	12.481%	$156.7535	$156.75	$156.75	$156.80
Purchase #7	$111.59	7.212%	$119.6379	$119.64	$119.65	$119.60
7 purchase totals =	$694.41		$760.4783	$760.47	$760.45	$760.40