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	$182.39	4.136%	$189.9337	$189.93	$189.95	$189.90
Purchase #2	$63.42	5.846%	$67.1275	$67.13	$67.15	$67.10
Purchase #3	$98.27	13.383%	$111.4215	$111.42	$111.40	$111.40
Purchase #4	$61.66	4.323%	$64.3256	$64.33	$64.35	$64.30
Purchase #5	$146.31	12.693%	$164.8811	$164.88	$164.90	$164.90
Purchase #6	$192.48	6.368%	$204.7371	$204.74	$204.75	$204.70
Purchase #7	$9.83	9.139%	$10.7284	$10.73	$10.75	$10.70
7 purchase totals =	$754.36		$813.1549	$813.16	$813.25	$813.00