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	$93.56	13.232%	$105.9399	$105.94	$105.95	$105.90
Purchase #2	$53.29	8.842%	$58.0019	$58.00	$58.00	$58.00
Purchase #3	$247.69	10.311%	$273.2293	$273.23	$273.25	$273.20
Purchase #4	$159.68	7.643%	$171.8843	$171.88	$171.90	$171.90
Purchase #5	$199.51	5.236%	$209.9563	$209.96	$209.95	$210.00
Purchase #6	$221.91	10.799%	$245.8741	$245.87	$245.85	$245.90
Purchase #7	$87.31	3.567%	$90.4243	$90.42	$90.40	$90.40
7 purchase totals =	$1,062.95		$1,155.3101	$1,155.30	$1,155.30	$1,155.30