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	$218.91	4.437%	$228.623	$228.62	$228.60	$228.60
Purchase #2	$216.29	6.148%	$229.5875	$229.59	$229.60	$229.60
Purchase #3	$170.46	11.631%	$190.2862	$190.29	$190.30	$190.30
Purchase #4	$37.32	13.867%	$42.4952	$42.50	$42.50	$42.50
Purchase #5	$29.94	9.722%	$32.8508	$32.85	$32.85	$32.90
Purchase #6	$155.96	5.180%	$164.0387	$164.04	$164.05	$164.00
Purchase #7	$209.33	8.687%	$227.5145	$227.51	$227.50	$227.50
7 purchase totals =	$1,038.21		$1,115.3959	$1,115.40	$1,115.40	$1,115.40