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	$98.34	10.755%	$108.9165	$108.92	$108.90	$108.90
Purchase #2	$204.64	7.410%	$219.8038	$219.80	$219.80	$219.80
Purchase #3	$79.78	11.870%	$89.2499	$89.25	$89.25	$89.20
Purchase #4	$247.88	13.417%	$281.1381	$281.14	$281.15	$281.10
Purchase #5	$122.30	4.278%	$127.532	$127.53	$127.55	$127.50
Purchase #6	$63.74	12.873%	$71.9453	$71.95	$71.95	$71.90
Purchase #7	$189.73	11.582%	$211.7045	$211.70	$211.70	$211.70
7 purchase totals =	$1,006.41		$1,110.2901	$1,110.29	$1,110.30	$1,110.10