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	$75.36	9.405%	$82.4476	$82.45	$82.45	$82.40
Purchase #2	$81.54	6.759%	$87.0513	$87.05	$87.05	$87.10
Purchase #3	$181.65	13.472%	$206.1219	$206.12	$206.10	$206.10
Purchase #4	$134.74	11.866%	$150.7282	$150.73	$150.75	$150.70
Purchase #5	$222.25	9.811%	$244.0549	$244.05	$244.05	$244.10
Purchase #6	$86.56	5.820%	$91.5978	$91.60	$91.60	$91.60
Purchase #7	$66.72	6.465%	$71.0334	$71.03	$71.05	$71.00
7 purchase totals =	$848.82		$933.0351	$933.03	$933.05	$933.00