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	$202.82	12.562%	$228.2982	$228.30	$228.30	$228.30
Purchase #2	$223.55	9.801%	$245.4601	$245.46	$245.45	$245.50
Purchase #3	$95.94	4.314%	$100.0789	$100.08	$100.10	$100.10
Purchase #4	$107.60	9.174%	$117.4712	$117.47	$117.45	$117.50
Purchase #5	$139.72	8.828%	$152.0545	$152.05	$152.05	$152.10
Purchase #6	$31.71	5.183%	$33.3535	$33.35	$33.35	$33.40
Purchase #7	$154.52	11.787%	$172.7333	$172.73	$172.75	$172.70
7 purchase totals =	$955.86		$1,049.4497	$1,049.44	$1,049.45	$1,049.60