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	$231.38	6.268%	$245.8829	$245.88	$245.90	$245.90
Purchase #2	$50.38	4.723%	$52.7594	$52.76	$52.75	$52.80
Purchase #3	$242.44	12.531%	$272.8202	$272.82	$272.80	$272.80
Purchase #4	$107.25	6.380%	$114.0926	$114.09	$114.10	$114.10
Purchase #5	$61.88	8.429%	$67.0959	$67.10	$67.10	$67.10
Purchase #6	$128.98	13.397%	$146.2595	$146.26	$146.25	$146.30
Purchase #7	$151.31	13.553%	$171.817	$171.82	$171.80	$171.80
7 purchase totals =	$973.62		$1,070.7275	$1,070.73	$1,070.70	$1,070.80