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	$194.90	5.114%	$204.8672	$204.87	$204.85	$204.90
Purchase #2	$77.28	7.287%	$82.9114	$82.91	$82.90	$82.90
Purchase #3	$243.55	8.743%	$264.8436	$264.84	$264.85	$264.80
Purchase #4	$219.25	10.129%	$241.4578	$241.46	$241.45	$241.50
Purchase #5	$243.42	6.451%	$259.123	$259.12	$259.10	$259.10
Purchase #6	$75.65	3.656%	$78.4158	$78.42	$78.40	$78.40
Purchase #7	$135.30	10.140%	$149.0194	$149.02	$149.00	$149.00
7 purchase totals =	$1,189.35		$1,280.6382	$1,280.64	$1,280.55	$1,280.60