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	$144.25	11.712%	$161.1446	$161.14	$161.15	$161.10
Purchase #2	$89.88	10.584%	$99.3929	$99.39	$99.40	$99.40
Purchase #3	$6.38	6.791%	$6.8133	$6.81	$6.80	$6.80
Purchase #4	$201.63	10.243%	$222.283	$222.28	$222.30	$222.30
Purchase #5	$78.39	5.449%	$82.6615	$82.66	$82.65	$82.70
Purchase #6	$227.73	6.764%	$243.1337	$243.13	$243.15	$243.10
Purchase #7	$224.26	8.472%	$243.2593	$243.26	$243.25	$243.30
7 purchase totals =	$972.52		$1,058.6883	$1,058.67	$1,058.70	$1,058.70