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	$158.55	4.359%	$165.4612	$165.46	$165.45	$165.50
Purchase #2	$223.49	12.833%	$252.1705	$252.17	$252.15	$252.20
Purchase #3	$80.52	9.696%	$88.3272	$88.33	$88.35	$88.30
Purchase #4	$25.71	11.688%	$28.715	$28.72	$28.70	$28.70
Purchase #5	$57.90	3.190%	$59.747	$59.75	$59.75	$59.70
Purchase #6	$240.91	8.229%	$260.7345	$260.73	$260.75	$260.70
Purchase #7	$237.49	3.261%	$245.2345	$245.23	$245.25	$245.20
7 purchase totals =	$1,024.57		$1,100.3899	$1,100.39	$1,100.40	$1,100.30