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	$245.55	4.454%	$256.4868	$256.49	$256.50	$256.50
Purchase #2	$29.68	12.774%	$33.4713	$33.47	$33.45	$33.50
Purchase #3	$94.75	4.775%	$99.2743	$99.27	$99.25	$99.30
Purchase #4	$246.29	9.819%	$270.4732	$270.47	$270.45	$270.50
Purchase #5	$154.56	13.671%	$175.6899	$175.69	$175.70	$175.70
Purchase #6	$130.86	11.158%	$145.4614	$145.46	$145.45	$145.50
Purchase #7	$165.99	3.106%	$171.1456	$171.15	$171.15	$171.10
7 purchase totals =	$1,067.68		$1,152.0025	$1,152.00	$1,151.95	$1,152.10