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	$109.90	7.697%	$118.359	$118.36	$118.35	$118.40
Purchase #2	$185.78	3.128%	$191.5912	$191.59	$191.60	$191.60
Purchase #3	$209.26	11.593%	$233.5195	$233.52	$233.50	$233.50
Purchase #4	$238.77	12.142%	$267.7615	$267.76	$267.75	$267.80
Purchase #5	$176.47	10.455%	$194.9199	$194.92	$194.90	$194.90
Purchase #6	$128.73	6.234%	$136.755	$136.76	$136.75	$136.80
Purchase #7	$48.47	9.173%	$52.9162	$52.92	$52.90	$52.90
7 purchase totals =	$1,097.38		$1,195.8223	$1,195.83	$1,195.75	$1,195.90