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	$69.52	4.173%	$72.4211	$72.42	$72.40	$72.40
Purchase #2	$149.71	11.867%	$167.4761	$167.48	$167.50	$167.50
Purchase #3	$236.88	9.251%	$258.7938	$258.79	$258.80	$258.80
Purchase #4	$154.97	8.127%	$167.5644	$167.56	$167.55	$167.60
Purchase #5	$160.63	13.109%	$181.687	$181.69	$181.70	$181.70
Purchase #6	$5.89	3.852%	$6.1169	$6.12	$6.10	$6.10
Purchase #7	$229.92	9.116%	$250.8795	$250.88	$250.90	$250.90
7 purchase totals =	$1,007.52		$1,104.9388	$1,104.94	$1,104.95	$1,105.00