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	$158.62	9.168%	$173.1623	$173.16	$173.15	$173.20
Purchase #2	$239.76	13.288%	$271.6193	$271.62	$271.60	$271.60
Purchase #3	$228.46	13.494%	$259.2884	$259.29	$259.30	$259.30
Purchase #4	$203.89	10.315%	$224.9213	$224.92	$224.90	$224.90
Purchase #5	$96.63	9.270%	$105.5876	$105.59	$105.60	$105.60
Purchase #6	$171.58	6.609%	$182.9197	$182.92	$182.90	$182.90
Purchase #7	$36.57	4.868%	$38.3502	$38.35	$38.35	$38.40
7 purchase totals =	$1,135.51		$1,255.8488	$1,255.85	$1,255.80	$1,255.90