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	$114.86	10.675%	$127.1213	$127.12	$127.10	$127.10
Purchase #2	$54.73	4.752%	$57.3308	$57.33	$57.35	$57.30
Purchase #3	$100.65	9.240%	$109.9501	$109.95	$109.95	$110.00
Purchase #4	$12.93	7.623%	$13.9157	$13.92	$13.90	$13.90
Purchase #5	$170.33	8.178%	$184.2596	$184.26	$184.25	$184.30
Purchase #6	$211.57	11.689%	$236.3004	$236.30	$236.30	$236.30
Purchase #7	$185.59	3.413%	$191.9242	$191.92	$191.90	$191.90
7 purchase totals =	$850.66		$920.8021	$920.80	$920.75	$920.80