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	$147.92	9.798%	$162.4132	$162.41	$162.40	$162.40
Purchase #2	$32.44	4.109%	$33.773	$33.77	$33.75	$33.80
Purchase #3	$212.39	13.220%	$240.468	$240.47	$240.45	$240.50
Purchase #4	$146.69	4.719%	$153.6123	$153.61	$153.60	$153.60
Purchase #5	$84.67	3.850%	$87.9298	$87.93	$87.95	$87.90
Purchase #6	$72.92	4.803%	$76.4223	$76.42	$76.40	$76.40
Purchase #7	$79.90	3.685%	$82.8443	$82.84	$82.85	$82.80
7 purchase totals =	$776.93		$837.4629	$837.45	$837.40	$837.40