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	$245.75	13.166%	$278.1054	$278.11	$278.10	$278.10
Purchase #2	$202.78	4.461%	$211.826	$211.83	$211.85	$211.80
Purchase #3	$98.72	12.785%	$111.3414	$111.34	$111.35	$111.30
Purchase #4	$14.53	3.130%	$14.9848	$14.98	$15.00	$15.00
Purchase #5	$85.74	9.812%	$94.1528	$94.15	$94.15	$94.20
Purchase #6	$200.43	6.654%	$213.7666	$213.77	$213.75	$213.80
Purchase #7	$147.69	12.665%	$166.3949	$166.39	$166.40	$166.40
7 purchase totals =	$995.64		$1,090.5719	$1,090.57	$1,090.60	$1,090.60