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	$79.35	13.506%	$90.067	$90.07	$90.05	$90.10
Purchase #2	$156.74	12.784%	$176.7776	$176.78	$176.80	$176.80
Purchase #3	$183.89	6.102%	$195.111	$195.11	$195.10	$195.10
Purchase #4	$61.37	10.600%	$67.8752	$67.88	$67.90	$67.90
Purchase #5	$180.59	7.637%	$194.3817	$194.38	$194.40	$194.40
Purchase #6	$139.90	5.843%	$148.0744	$148.07	$148.05	$148.10
Purchase #7	$154.61	6.331%	$164.3984	$164.40	$164.40	$164.40
7 purchase totals =	$956.45		$1,036.6853	$1,036.69	$1,036.70	$1,036.80