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	$111.43	6.612%	$118.7978	$118.80	$118.80	$118.80
Purchase #2	$59.53	13.150%	$67.3582	$67.36	$67.35	$67.40
Purchase #3	$142.69	10.133%	$157.1488	$157.15	$157.15	$157.10
Purchase #4	$183.29	7.184%	$196.4576	$196.46	$196.45	$196.50
Purchase #5	$130.50	11.275%	$145.2139	$145.21	$145.20	$145.20
Purchase #6	$59.76	7.517%	$64.2522	$64.25	$64.25	$64.30
Purchase #7	$199.59	12.450%	$224.439	$224.44	$224.45	$224.40
7 purchase totals =	$886.79		$973.6675	$973.67	$973.65	$973.70