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	$40.48	4.650%	$42.3623	$42.36	$42.35	$42.40
Purchase #2	$136.34	4.778%	$142.8543	$142.85	$142.85	$142.90
Purchase #3	$101.96	13.647%	$115.8745	$115.87	$115.85	$115.90
Purchase #4	$156.33	10.507%	$172.7556	$172.76	$172.75	$172.80
Purchase #5	$233.56	8.141%	$252.5741	$252.57	$252.55	$252.60
Purchase #6	$153.59	9.844%	$168.7094	$168.71	$168.70	$168.70
Purchase #7	$159.57	8.343%	$172.8829	$172.88	$172.90	$172.90
7 purchase totals =	$981.83		$1,068.0131	$1,068.00	$1,067.95	$1,068.20