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	$192.76	9.744%	$211.5425	$211.54	$211.55	$211.50
Purchase #2	$162.76	4.178%	$169.5601	$169.56	$169.55	$169.60
Purchase #3	$232.76	9.650%	$255.2213	$255.22	$255.20	$255.20
Purchase #4	$240.38	10.195%	$264.8867	$264.89	$264.90	$264.90
Purchase #5	$60.95	11.211%	$67.7831	$67.78	$67.80	$67.80
Purchase #6	$99.81	4.573%	$104.3743	$104.37	$104.35	$104.40
Purchase #7	$19.81	5.699%	$20.939	$20.94	$20.95	$20.90
7 purchase totals =	$1,009.23		$1,094.3070	$1,094.30	$1,094.30	$1,094.30