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	$144.26	5.543%	$152.2563	$152.26	$152.25	$152.30
Purchase #2	$31.89	13.321%	$36.1381	$36.14	$36.15	$36.10
Purchase #3	$48.55	6.603%	$51.7558	$51.76	$51.75	$51.80
Purchase #4	$68.88	5.393%	$72.5947	$72.59	$72.60	$72.60
Purchase #5	$223.56	9.494%	$244.7848	$244.78	$244.80	$244.80
Purchase #6	$29.84	11.835%	$33.3716	$33.37	$33.35	$33.40
Purchase #7	$79.34	5.371%	$83.6014	$83.60	$83.60	$83.60
7 purchase totals =	$626.32		$674.5027	$674.50	$674.50	$674.60