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	$198.75	6.344%	$211.3587	$211.36	$211.35	$211.40
Purchase #2	$64.31	10.308%	$70.9391	$70.94	$70.95	$70.90
Purchase #3	$235.80	8.318%	$255.4138	$255.41	$255.40	$255.40
Purchase #4	$136.47	8.713%	$148.3606	$148.36	$148.35	$148.40
Purchase #5	$131.99	4.492%	$137.919	$137.92	$137.90	$137.90
Purchase #6	$174.56	7.844%	$188.2525	$188.25	$188.25	$188.30
Purchase #7	$138.85	12.623%	$156.377	$156.38	$156.40	$156.40
7 purchase totals =	$1,080.73		$1,168.6207	$1,168.62	$1,168.60	$1,168.70