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	$99.71	11.566%	$111.2425	$111.24	$111.25	$111.20
Purchase #2	$20.51	9.490%	$22.4564	$22.46	$22.45	$22.50
Purchase #3	$92.89	4.380%	$96.9586	$96.96	$96.95	$97.00
Purchase #4	$96.80	8.232%	$104.7686	$104.77	$104.75	$104.80
Purchase #5	$51.36	11.848%	$57.4451	$57.45	$57.45	$57.40
Purchase #6	$184.50	11.712%	$206.1086	$206.11	$206.10	$206.10
Purchase #7	$59.35	5.151%	$62.4071	$62.41	$62.40	$62.40
7 purchase totals =	$605.12		$661.3869	$661.40	$661.35	$661.40