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	$148.77	6.692%	$158.7257	$158.73	$158.75	$158.70
Purchase #2	$151.80	8.564%	$164.8002	$164.80	$164.80	$164.80
Purchase #3	$193.26	11.483%	$215.452	$215.45	$215.45	$215.50
Purchase #4	$212.44	4.783%	$222.601	$222.60	$222.60	$222.60
Purchase #5	$88.91	6.556%	$94.7389	$94.74	$94.75	$94.70
Purchase #6	$93.60	3.807%	$97.1634	$97.16	$97.15	$97.20
Purchase #7	$91.55	10.150%	$100.8423	$100.84	$100.85	$100.80
7 purchase totals =	$980.33		$1,054.3235	$1,054.32	$1,054.35	$1,054.30