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	$145.58	6.250%	$154.6788	$154.68	$154.70	$154.70
Purchase #2	$111.29	10.628%	$123.1179	$123.12	$123.10	$123.10
Purchase #3	$159.30	6.732%	$170.0241	$170.02	$170.00	$170.00
Purchase #4	$136.96	10.556%	$151.4175	$151.42	$151.40	$151.40
Purchase #5	$125.83	13.581%	$142.919	$142.92	$142.90	$142.90
Purchase #6	$195.93	5.218%	$206.1536	$206.15	$206.15	$206.20
Purchase #7	$55.84	12.395%	$62.7614	$62.76	$62.75	$62.80
7 purchase totals =	$930.73		$1,011.0723	$1,011.07	$1,011.00	$1,011.10