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	$153.62	4.578%	$160.6527	$160.65	$160.65	$160.70
Purchase #2	$70.92	12.603%	$79.858	$79.86	$79.85	$79.90
Purchase #3	$27.65	4.256%	$28.8268	$28.83	$28.85	$28.80
Purchase #4	$105.93	10.398%	$116.9446	$116.94	$116.95	$116.90
Purchase #5	$74.60	12.496%	$83.922	$83.92	$83.90	$83.90
Purchase #6	$185.63	12.870%	$209.5206	$209.52	$209.50	$209.50
Purchase #7	$103.43	8.870%	$112.6042	$112.60	$112.60	$112.60
7 purchase totals =	$721.78		$792.3289	$792.32	$792.30	$792.30