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	$125.72	3.798%	$130.4948	$130.49	$130.50	$130.50
Purchase #2	$203.53	9.214%	$222.2833	$222.28	$222.30	$222.30
Purchase #3	$135.96	7.373%	$145.9843	$145.98	$146.00	$146.00
Purchase #4	$224.91	5.564%	$237.424	$237.42	$237.40	$237.40
Purchase #5	$38.72	10.804%	$42.9033	$42.90	$42.90	$42.90
Purchase #6	$163.32	4.781%	$171.1283	$171.13	$171.15	$171.10
Purchase #7	$105.54	5.854%	$111.7183	$111.72	$111.70	$111.70
7 purchase totals =	$997.70		$1,061.9363	$1,061.92	$1,061.95	$1,061.90