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	$50.30	5.286%	$52.9589	$52.96	$52.95	$53.00
Purchase #2	$160.44	6.651%	$171.1109	$171.11	$171.10	$171.10
Purchase #3	$37.36	11.287%	$41.5768	$41.58	$41.60	$41.60
Purchase #4	$246.92	11.432%	$275.1479	$275.15	$275.15	$275.10
Purchase #5	$159.69	13.156%	$180.6988	$180.70	$180.70	$180.70
Purchase #6	$149.46	12.431%	$168.0394	$168.04	$168.05	$168.00
Purchase #7	$217.75	9.301%	$238.0029	$238.00	$238.00	$238.00
7 purchase totals =	$1,021.92		$1,127.5356	$1,127.54	$1,127.55	$1,127.50