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	$107.69	10.776%	$119.2947	$119.29	$119.30	$119.30
Purchase #2	$107.90	7.427%	$115.9137	$115.91	$115.90	$115.90
Purchase #3	$121.59	7.666%	$130.9111	$130.91	$130.90	$130.90
Purchase #4	$105.63	5.429%	$111.3647	$111.36	$111.35	$111.40
Purchase #5	$131.53	4.625%	$137.6133	$137.61	$137.60	$137.60
Purchase #6	$200.26	4.640%	$209.5521	$209.55	$209.55	$209.60
Purchase #7	$159.86	10.482%	$176.6165	$176.62	$176.60	$176.60
7 purchase totals =	$934.46		$1,001.2661	$1,001.25	$1,001.20	$1,001.30