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	$218.54	11.609%	$243.9103	$243.91	$243.90	$243.90
Purchase #2	$243.48	9.176%	$265.8217	$265.82	$265.80	$265.80
Purchase #3	$91.62	5.382%	$96.551	$96.55	$96.55	$96.60
Purchase #4	$207.52	12.543%	$233.5492	$233.55	$233.55	$233.50
Purchase #5	$152.72	12.667%	$172.065	$172.07	$172.05	$172.10
Purchase #6	$70.56	12.672%	$79.5014	$79.50	$79.50	$79.50
Purchase #7	$67.57	13.814%	$76.9041	$76.90	$76.90	$76.90
7 purchase totals =	$1,052.01		$1,168.3027	$1,168.30	$1,168.25	$1,168.30