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	$10.86	7.510%	$11.6756	$11.68	$11.70	$11.70
Purchase #2	$21.89	4.460%	$22.8663	$22.87	$22.85	$22.90
Purchase #3	$213.33	7.471%	$229.2679	$229.27	$229.25	$229.30
Purchase #4	$28.97	7.576%	$31.1648	$31.16	$31.15	$31.20
Purchase #5	$79.90	7.527%	$85.9141	$85.91	$85.90	$85.90
Purchase #6	$229.39	5.607%	$242.2519	$242.25	$242.25	$242.30
Purchase #7	$167.56	11.337%	$186.5563	$186.56	$186.55	$186.60
7 purchase totals =	$751.90		$809.6969	$809.70	$809.65	$809.90