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	$212.38	7.716%	$228.7672	$228.77	$228.75	$228.80
Purchase #2	$156.45	9.679%	$171.5928	$171.59	$171.60	$171.60
Purchase #3	$126.43	8.585%	$137.284	$137.28	$137.30	$137.30
Purchase #4	$163.66	7.437%	$175.8314	$175.83	$175.85	$175.80
Purchase #5	$81.42	4.543%	$85.1189	$85.12	$85.10	$85.10
Purchase #6	$49.78	8.793%	$54.1572	$54.16	$54.15	$54.20
Purchase #7	$37.65	6.729%	$40.1835	$40.18	$40.20	$40.20
7 purchase totals =	$827.77		$892.9350	$892.93	$892.95	$893.00