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	$25.37	7.826%	$27.3555	$27.36	$27.35	$27.40
Purchase #2	$160.46	11.805%	$179.4023	$179.40	$179.40	$179.40
Purchase #3	$245.50	5.285%	$258.4747	$258.47	$258.45	$258.50
Purchase #4	$174.98	7.742%	$188.527	$188.53	$188.55	$188.50
Purchase #5	$98.53	6.315%	$104.7522	$104.75	$104.75	$104.80
Purchase #6	$34.78	7.803%	$37.4939	$37.49	$37.50	$37.50
Purchase #7	$158.72	4.108%	$165.2402	$165.24	$165.25	$165.20
7 purchase totals =	$898.34		$961.2458	$961.24	$961.25	$961.30