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	$120.47	5.458%	$127.0453	$127.05	$127.05	$127.00
Purchase #2	$113.98	11.499%	$127.0866	$127.09	$127.10	$127.10
Purchase #3	$194.95	9.117%	$212.7236	$212.72	$212.70	$212.70
Purchase #4	$237.76	12.621%	$267.7677	$267.77	$267.75	$267.80
Purchase #5	$84.93	6.651%	$90.5787	$90.58	$90.60	$90.60
Purchase #6	$172.60	6.500%	$183.819	$183.82	$183.80	$183.80
Purchase #7	$127.55	5.375%	$134.4058	$134.41	$134.40	$134.40
7 purchase totals =	$1,052.24		$1,143.4267	$1,143.44	$1,143.40	$1,143.40