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	$95.83	3.533%	$99.2157	$99.22	$99.20	$99.20
Purchase #2	$106.44	13.591%	$120.9063	$120.91	$120.90	$120.90
Purchase #3	$70.67	4.332%	$73.7314	$73.73	$73.75	$73.70
Purchase #4	$202.51	13.622%	$230.0959	$230.10	$230.10	$230.10
Purchase #5	$119.55	6.826%	$127.7105	$127.71	$127.70	$127.70
Purchase #6	$215.95	13.736%	$245.6129	$245.61	$245.60	$245.60
Purchase #7	$115.46	10.143%	$127.1711	$127.17	$127.15	$127.20
7 purchase totals =	$926.41		$1,024.4438	$1,024.45	$1,024.40	$1,024.40