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	$75.91	9.208%	$82.8998	$82.90	$82.90	$82.90
Purchase #2	$227.80	6.741%	$243.156	$243.16	$243.15	$243.20
Purchase #3	$189.84	3.439%	$196.3686	$196.37	$196.35	$196.40
Purchase #4	$221.54	4.850%	$232.2847	$232.28	$232.30	$232.30
Purchase #5	$22.84	9.804%	$25.0792	$25.08	$25.10	$25.10
Purchase #6	$156.53	6.358%	$166.4822	$166.48	$166.50	$166.50
Purchase #7	$151.39	7.307%	$162.4521	$162.45	$162.45	$162.50
7 purchase totals =	$1,045.85		$1,108.7226	$1,108.72	$1,108.75	$1,108.90