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	$198.33	10.728%	$219.6068	$219.61	$219.60	$219.60
Purchase #2	$117.28	5.533%	$123.7691	$123.77	$123.75	$123.80
Purchase #3	$142.66	4.428%	$148.977	$148.98	$149.00	$149.00
Purchase #4	$150.29	12.662%	$169.3197	$169.32	$169.30	$169.30
Purchase #5	$105.47	13.671%	$119.8888	$119.89	$119.90	$119.90
Purchase #6	$49.73	8.569%	$53.9914	$53.99	$54.00	$54.00
Purchase #7	$111.78	7.384%	$120.0338	$120.03	$120.05	$120.00
7 purchase totals =	$875.54		$955.5866	$955.59	$955.60	$955.60