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	$47.91	11.709%	$53.5198	$53.52	$53.50	$53.50
Purchase #2	$77.35	6.840%	$82.6407	$82.64	$82.65	$82.60
Purchase #3	$56.74	7.221%	$60.8372	$60.84	$60.85	$60.80
Purchase #4	$203.66	11.603%	$227.2907	$227.29	$227.30	$227.30
Purchase #5	$64.36	12.732%	$72.5543	$72.55	$72.55	$72.60
Purchase #6	$196.64	7.339%	$211.0714	$211.07	$211.05	$211.10
Purchase #7	$213.90	12.355%	$240.3273	$240.33	$240.35	$240.30
7 purchase totals =	$860.56		$948.2414	$948.24	$948.25	$948.20