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	$135.94	11.445%	$151.4983	$151.50	$151.50	$151.50
Purchase #2	$220.46	3.396%	$227.9468	$227.95	$227.95	$227.90
Purchase #3	$30.52	9.611%	$33.4533	$33.45	$33.45	$33.50
Purchase #4	$223.88	11.837%	$250.3807	$250.38	$250.40	$250.40
Purchase #5	$227.33	10.564%	$251.3451	$251.35	$251.35	$251.30
Purchase #6	$203.36	3.871%	$211.2321	$211.23	$211.25	$211.20
Purchase #7	$162.83	6.150%	$172.844	$172.84	$172.85	$172.80
7 purchase totals =	$1,204.32		$1,298.7003	$1,298.70	$1,298.75	$1,298.60