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	$220.89	7.837%	$238.2011	$238.20	$238.20	$238.20
Purchase #2	$40.30	3.767%	$41.8181	$41.82	$41.80	$41.80
Purchase #3	$44.84	13.197%	$50.7575	$50.76	$50.75	$50.80
Purchase #4	$248.48	7.186%	$266.3358	$266.34	$266.35	$266.30
Purchase #5	$122.91	7.254%	$131.8259	$131.83	$131.85	$131.80
Purchase #6	$156.37	10.178%	$172.2853	$172.29	$172.30	$172.30
Purchase #7	$209.77	12.169%	$235.2969	$235.30	$235.30	$235.30
7 purchase totals =	$1,043.56		$1,136.5206	$1,136.54	$1,136.55	$1,136.50