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	$54.99	13.724%	$62.5368	$62.54	$62.55	$62.50
Purchase #2	$204.69	12.819%	$230.9292	$230.93	$230.95	$230.90
Purchase #3	$250.35	12.359%	$281.2908	$281.29	$281.30	$281.30
Purchase #4	$100.33	4.799%	$105.1448	$105.14	$105.15	$105.10
Purchase #5	$92.87	5.818%	$98.2732	$98.27	$98.25	$98.30
Purchase #6	$137.66	6.265%	$146.2844	$146.28	$146.30	$146.30
Purchase #7	$237.46	4.810%	$248.8818	$248.88	$248.90	$248.90
7 purchase totals =	$1,078.35		$1,173.3410	$1,173.33	$1,173.40	$1,173.30