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	$247.78	8.262%	$268.2516	$268.25	$268.25	$268.30
Purchase #2	$73.45	6.540%	$78.2536	$78.25	$78.25	$78.30
Purchase #3	$48.75	9.281%	$53.2745	$53.27	$53.25	$53.30
Purchase #4	$158.33	7.657%	$170.4533	$170.45	$170.45	$170.50
Purchase #5	$211.91	5.318%	$223.1794	$223.18	$223.20	$223.20
Purchase #6	$213.43	11.179%	$237.2893	$237.29	$237.30	$237.30
Purchase #7	$102.74	11.450%	$114.5037	$114.50	$114.50	$114.50
7 purchase totals =	$1,056.39		$1,145.2054	$1,145.19	$1,145.20	$1,145.40