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	$153.50	5.548%	$162.0162	$162.02	$162.00	$162.00
Purchase #2	$180.70	13.238%	$204.6211	$204.62	$204.60	$204.60
Purchase #3	$250.26	7.250%	$268.4039	$268.40	$268.40	$268.40
Purchase #4	$83.31	7.736%	$89.7549	$89.75	$89.75	$89.80
Purchase #5	$60.42	10.564%	$66.8028	$66.80	$66.80	$66.80
Purchase #6	$55.90	3.431%	$57.8179	$57.82	$57.80	$57.80
Purchase #7	$98.94	4.731%	$103.6209	$103.62	$103.60	$103.60
7 purchase totals =	$883.03		$953.0377	$953.03	$952.95	$953.00