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	$61.72	5.494%	$65.1109	$65.11	$65.10	$65.10
Purchase #2	$206.50	3.682%	$214.1033	$214.10	$214.10	$214.10
Purchase #3	$14.76	4.403%	$15.4099	$15.41	$15.40	$15.40
Purchase #4	$23.83	13.805%	$27.1197	$27.12	$27.10	$27.10
Purchase #5	$77.71	5.816%	$82.2296	$82.23	$82.25	$82.20
Purchase #6	$184.62	7.570%	$198.5957	$198.60	$198.60	$198.60
Purchase #7	$186.84	6.470%	$198.9285	$198.93	$198.95	$198.90
7 purchase totals =	$755.98		$801.4976	$801.50	$801.50	$801.40