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	$89.56	13.469%	$101.6228	$101.62	$101.60	$101.60
Purchase #2	$28.57	13.604%	$32.4567	$32.46	$32.45	$32.50
Purchase #3	$89.77	3.237%	$92.6759	$92.68	$92.70	$92.70
Purchase #4	$105.72	8.364%	$114.5624	$114.56	$114.55	$114.60
Purchase #5	$195.81	7.745%	$210.9755	$210.98	$211.00	$211.00
Purchase #6	$66.52	7.231%	$71.3301	$71.33	$71.35	$71.30
Purchase #7	$151.73	11.261%	$168.8163	$168.82	$168.80	$168.80
7 purchase totals =	$727.68		$792.4397	$792.45	$792.45	$792.50