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	$67.57	4.108%	$70.3458	$70.35	$70.35	$70.30
Purchase #2	$137.36	9.636%	$150.596	$150.60	$150.60	$150.60
Purchase #3	$145.77	11.548%	$162.6035	$162.60	$162.60	$162.60
Purchase #4	$13.33	10.659%	$14.7508	$14.75	$14.75	$14.80
Purchase #5	$194.41	3.148%	$200.53	$200.53	$200.55	$200.50
Purchase #6	$37.46	11.207%	$41.6581	$41.66	$41.65	$41.70
Purchase #7	$82.79	8.183%	$89.5647	$89.56	$89.55	$89.60
7 purchase totals =	$678.69		$730.0489	$730.05	$730.05	$730.10