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	$53.25	11.766%	$59.5154	$59.52	$59.50	$59.50
Purchase #2	$40.79	9.302%	$44.5843	$44.58	$44.60	$44.60
Purchase #3	$67.60	6.384%	$71.9156	$71.92	$71.90	$71.90
Purchase #4	$33.86	3.685%	$35.1077	$35.11	$35.10	$35.10
Purchase #5	$179.88	4.572%	$188.1041	$188.10	$188.10	$188.10
Purchase #6	$72.40	6.854%	$77.3623	$77.36	$77.35	$77.40
Purchase #7	$28.26	11.764%	$31.5845	$31.58	$31.60	$31.60
7 purchase totals =	$476.04		$508.1739	$508.17	$508.15	$508.20