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	$216.29	5.244%	$227.6322	$227.63	$227.65	$227.60
Purchase #2	$124.69	6.842%	$133.2213	$133.22	$133.20	$133.20
Purchase #3	$79.31	11.380%	$88.3355	$88.34	$88.35	$88.30
Purchase #4	$85.38	3.710%	$88.5476	$88.55	$88.55	$88.50
Purchase #5	$212.32	12.500%	$238.86	$238.86	$238.85	$238.90
Purchase #6	$79.80	11.671%	$89.1135	$89.11	$89.10	$89.10
Purchase #7	$206.97	7.633%	$222.768	$222.77	$222.75	$222.80
7 purchase totals =	$1,004.76		$1,088.4781	$1,088.48	$1,088.45	$1,088.40