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	$243.90	13.614%	$277.1045	$277.10	$277.10	$277.10
Purchase #2	$191.77	13.814%	$218.2611	$218.26	$218.25	$218.30
Purchase #3	$24.31	4.768%	$25.4691	$25.47	$25.45	$25.50
Purchase #4	$105.40	6.566%	$112.3206	$112.32	$112.30	$112.30
Purchase #5	$29.99	9.263%	$32.768	$32.77	$32.75	$32.80
Purchase #6	$63.76	4.326%	$66.5183	$66.52	$66.50	$66.50
Purchase #7	$161.55	6.682%	$172.3448	$172.34	$172.35	$172.30
7 purchase totals =	$820.68		$904.7864	$904.78	$904.70	$904.80