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	$55.59	11.624%	$62.0518	$62.05	$62.05	$62.10
Purchase #2	$156.58	6.374%	$166.5604	$166.56	$166.55	$166.60
Purchase #3	$184.73	8.160%	$199.804	$199.80	$199.80	$199.80
Purchase #4	$105.36	10.609%	$116.5376	$116.54	$116.55	$116.50
Purchase #5	$149.59	8.368%	$162.1077	$162.11	$162.10	$162.10
Purchase #6	$86.34	4.693%	$90.3919	$90.39	$90.40	$90.40
Purchase #7	$78.54	6.393%	$83.5611	$83.56	$83.55	$83.60
7 purchase totals =	$816.73		$881.0145	$881.01	$881.00	$881.10