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	$83.31	7.758%	$89.7732	$89.77	$89.75	$89.80
Purchase #2	$50.51	3.452%	$52.2536	$52.25	$52.25	$52.30
Purchase #3	$45.93	10.441%	$50.7256	$50.73	$50.75	$50.70
Purchase #4	$138.37	8.873%	$150.6476	$150.65	$150.65	$150.60
Purchase #5	$220.29	7.695%	$237.2413	$237.24	$237.25	$237.20
Purchase #6	$160.86	12.802%	$181.4533	$181.45	$181.45	$181.50
Purchase #7	$80.79	6.626%	$86.1431	$86.14	$86.15	$86.10
7 purchase totals =	$780.06		$848.2377	$848.23	$848.25	$848.20