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	$58.29	5.816%	$61.6801	$61.68	$61.70	$61.70
Purchase #2	$86.39	4.238%	$90.0512	$90.05	$90.05	$90.10
Purchase #3	$136.41	4.484%	$142.5266	$142.53	$142.55	$142.50
Purchase #4	$143.44	8.238%	$155.2566	$155.26	$155.25	$155.30
Purchase #5	$78.79	8.216%	$85.2634	$85.26	$85.25	$85.30
Purchase #6	$9.66	6.743%	$10.3114	$10.31	$10.30	$10.30
Purchase #7	$149.77	3.693%	$155.301	$155.30	$155.30	$155.30
7 purchase totals =	$662.75		$700.3903	$700.39	$700.40	$700.50