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	$218.71	6.280%	$232.445	$232.45	$232.45	$232.40
Purchase #2	$48.98	6.182%	$52.0079	$52.01	$52.00	$52.00
Purchase #3	$67.32	7.696%	$72.5009	$72.50	$72.50	$72.50
Purchase #4	$80.59	13.852%	$91.7533	$91.75	$91.75	$91.80
Purchase #5	$26.65	11.566%	$29.7323	$29.73	$29.75	$29.70
Purchase #6	$139.44	13.852%	$158.7552	$158.76	$158.75	$158.80
Purchase #7	$159.52	11.757%	$178.2748	$178.27	$178.25	$178.30
7 purchase totals =	$741.21		$815.4694	$815.47	$815.45	$815.50