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	$237.53	7.844%	$256.1619	$256.16	$256.15	$256.20
Purchase #2	$98.48	8.845%	$107.1906	$107.19	$107.20	$107.20
Purchase #3	$135.41	12.308%	$152.0763	$152.08	$152.10	$152.10
Purchase #4	$158.27	5.103%	$166.3465	$166.35	$166.35	$166.30
Purchase #5	$176.27	11.392%	$196.3507	$196.35	$196.35	$196.40
Purchase #6	$110.51	8.422%	$119.8172	$119.82	$119.80	$119.80
Purchase #7	$174.72	7.495%	$187.8153	$187.82	$187.80	$187.80
7 purchase totals =	$1,091.19		$1,185.7585	$1,185.77	$1,185.75	$1,185.80