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	$105.30	10.281%	$116.1259	$116.13	$116.15	$116.10
Purchase #2	$83.32	6.644%	$88.8558	$88.86	$88.85	$88.90
Purchase #3	$239.73	12.254%	$269.1065	$269.11	$269.10	$269.10
Purchase #4	$69.83	13.388%	$79.1788	$79.18	$79.20	$79.20
Purchase #5	$143.63	11.267%	$159.8128	$159.81	$159.80	$159.80
Purchase #6	$76.78	12.410%	$86.3084	$86.31	$86.30	$86.30
Purchase #7	$196.47	11.802%	$219.6574	$219.66	$219.65	$219.70
7 purchase totals =	$915.06		$1,019.0456	$1,019.06	$1,019.05	$1,019.10