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	$168.77	11.761%	$188.619	$188.62	$188.60	$188.60
Purchase #2	$176.66	13.167%	$199.9208	$199.92	$199.90	$199.90
Purchase #3	$185.72	10.292%	$204.8343	$204.83	$204.85	$204.80
Purchase #4	$43.38	9.430%	$47.4707	$47.47	$47.45	$47.50
Purchase #5	$82.73	3.494%	$85.6206	$85.62	$85.60	$85.60
Purchase #6	$98.70	7.317%	$105.9219	$105.92	$105.90	$105.90
Purchase #7	$162.31	6.836%	$173.4055	$173.41	$173.40	$173.40
7 purchase totals =	$918.27		$1,005.7928	$1,005.79	$1,005.70	$1,005.70