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	$137.88	9.582%	$151.0917	$151.09	$151.10	$151.10
Purchase #2	$100.90	5.361%	$106.3092	$106.31	$106.30	$106.30
Purchase #3	$35.86	5.214%	$37.7297	$37.73	$37.75	$37.70
Purchase #4	$53.90	6.579%	$57.4461	$57.45	$57.45	$57.40
Purchase #5	$154.40	11.755%	$172.5497	$172.55	$172.55	$172.50
Purchase #6	$210.31	5.518%	$221.9149	$221.91	$221.90	$221.90
Purchase #7	$59.40	4.601%	$62.133	$62.13	$62.15	$62.10
7 purchase totals =	$752.65		$809.1743	$809.17	$809.20	$809.00