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	$54.90	7.868%	$59.2195	$59.22	$59.20	$59.20
Purchase #2	$33.63	6.322%	$35.7561	$35.76	$35.75	$35.80
Purchase #3	$79.77	12.102%	$89.4238	$89.42	$89.40	$89.40
Purchase #4	$177.45	4.576%	$185.5701	$185.57	$185.55	$185.60
Purchase #5	$67.79	13.635%	$77.0332	$77.03	$77.05	$77.00
Purchase #6	$181.64	7.791%	$195.7916	$195.79	$195.80	$195.80
Purchase #7	$56.29	13.699%	$64.0012	$64.00	$64.00	$64.00
7 purchase totals =	$651.47		$706.7955	$706.79	$706.75	$706.80