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	$121.42	4.643%	$127.0575	$127.06	$127.05	$127.10
Purchase #2	$223.26	12.766%	$251.7614	$251.76	$251.75	$251.80
Purchase #3	$211.62	13.468%	$240.121	$240.12	$240.10	$240.10
Purchase #4	$119.87	10.749%	$132.7548	$132.75	$132.75	$132.80
Purchase #5	$130.78	9.127%	$142.7163	$142.72	$142.70	$142.70
Purchase #6	$186.93	5.252%	$196.7476	$196.75	$196.75	$196.70
Purchase #7	$19.66	3.831%	$20.4132	$20.41	$20.40	$20.40
7 purchase totals =	$1,013.54		$1,111.5718	$1,111.57	$1,111.50	$1,111.60