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	$55.61	10.325%	$61.3517	$61.35	$61.35	$61.40
Purchase #2	$195.96	6.650%	$208.9913	$208.99	$209.00	$209.00
Purchase #3	$153.83	10.745%	$170.359	$170.36	$170.35	$170.40
Purchase #4	$125.28	9.784%	$137.5374	$137.54	$137.55	$137.50
Purchase #5	$248.90	7.715%	$268.1026	$268.10	$268.10	$268.10
Purchase #6	$28.42	10.761%	$31.4783	$31.48	$31.50	$31.50
Purchase #7	$245.82	13.453%	$278.8902	$278.89	$278.90	$278.90
7 purchase totals =	$1,053.82		$1,156.7105	$1,156.71	$1,156.75	$1,156.80