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	$38.50	9.264%	$42.0666	$42.07	$42.05	$42.10
Purchase #2	$202.43	12.687%	$228.1123	$228.11	$228.10	$228.10
Purchase #3	$213.95	3.820%	$222.1229	$222.12	$222.10	$222.10
Purchase #4	$90.60	9.298%	$99.024	$99.02	$99.00	$99.00
Purchase #5	$60.69	11.397%	$67.6068	$67.61	$67.60	$67.60
Purchase #6	$223.61	9.130%	$244.0256	$244.03	$244.05	$244.00
Purchase #7	$249.54	13.343%	$282.8361	$282.84	$282.85	$282.80
7 purchase totals =	$1,079.32		$1,185.7943	$1,185.80	$1,185.75	$1,185.70