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	$157.48	9.679%	$172.7225	$172.72	$172.70	$172.70
Purchase #2	$52.92	4.755%	$55.4363	$55.44	$55.45	$55.40
Purchase #3	$54.64	9.495%	$59.8281	$59.83	$59.85	$59.80
Purchase #4	$195.93	12.419%	$220.2625	$220.26	$220.25	$220.30
Purchase #5	$155.77	6.543%	$165.962	$165.96	$165.95	$166.00
Purchase #6	$238.76	10.242%	$263.2138	$263.21	$263.20	$263.20
Purchase #7	$123.50	7.542%	$132.8144	$132.81	$132.80	$132.80
7 purchase totals =	$979.00		$1,070.2396	$1,070.23	$1,070.20	$1,070.20