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	$132.75	13.834%	$151.1146	$151.11	$151.10	$151.10
Purchase #2	$20.61	4.556%	$21.549	$21.55	$21.55	$21.50
Purchase #3	$89.54	11.773%	$100.0815	$100.08	$100.10	$100.10
Purchase #4	$27.33	11.609%	$30.5027	$30.50	$30.50	$30.50
Purchase #5	$13.56	5.270%	$14.2746	$14.27	$14.25	$14.30
Purchase #6	$109.92	3.461%	$113.7243	$113.72	$113.70	$113.70
Purchase #7	$151.46	11.197%	$168.419	$168.42	$168.40	$168.40
7 purchase totals =	$545.17		$599.6657	$599.65	$599.60	$599.60