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	$210.30	8.784%	$228.7728	$228.77	$228.75	$228.80
Purchase #2	$164.70	8.314%	$178.3932	$178.39	$178.40	$178.40
Purchase #3	$150.91	7.846%	$162.7504	$162.75	$162.75	$162.80
Purchase #4	$18.36	11.463%	$20.4646	$20.46	$20.45	$20.50
Purchase #5	$148.45	5.874%	$157.17	$157.17	$157.15	$157.20
Purchase #6	$118.51	9.173%	$129.3809	$129.38	$129.40	$129.40
Purchase #7	$206.34	8.118%	$223.0907	$223.09	$223.10	$223.10
7 purchase totals =	$1,017.57		$1,100.0226	$1,100.01	$1,100.00	$1,100.20