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	$64.54	4.773%	$67.6205	$67.62	$67.60	$67.60
Purchase #2	$159.94	3.327%	$165.2612	$165.26	$165.25	$165.30
Purchase #3	$170.68	6.205%	$181.2707	$181.27	$181.25	$181.30
Purchase #4	$250.98	9.110%	$273.8443	$273.84	$273.85	$273.80
Purchase #5	$164.57	9.309%	$179.8898	$179.89	$179.90	$179.90
Purchase #6	$49.41	11.287%	$54.9869	$54.99	$55.00	$55.00
Purchase #7	$201.41	7.685%	$216.8884	$216.89	$216.90	$216.90
7 purchase totals =	$1,061.53		$1,139.7618	$1,139.76	$1,139.75	$1,139.80