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	$92.82	11.806%	$103.7783	$103.78	$103.80	$103.80
Purchase #2	$43.47	6.504%	$46.2973	$46.30	$46.30	$46.30
Purchase #3	$44.69	3.302%	$46.1657	$46.17	$46.15	$46.20
Purchase #4	$231.30	10.598%	$255.8132	$255.81	$255.80	$255.80
Purchase #5	$248.52	5.781%	$262.8869	$262.89	$262.90	$262.90
Purchase #6	$45.25	11.329%	$50.3764	$50.38	$50.40	$50.40
Purchase #7	$198.74	7.308%	$213.2639	$213.26	$213.25	$213.30
7 purchase totals =	$904.79		$978.5817	$978.59	$978.60	$978.70