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	$106.46	4.345%	$111.0857	$111.09	$111.10	$111.10
Purchase #2	$63.28	13.539%	$71.8475	$71.85	$71.85	$71.80
Purchase #3	$83.37	6.842%	$89.0742	$89.07	$89.05	$89.10
Purchase #4	$157.52	11.292%	$175.3072	$175.31	$175.30	$175.30
Purchase #5	$179.33	4.531%	$187.4554	$187.46	$187.45	$187.50
Purchase #6	$186.99	7.292%	$200.6253	$200.63	$200.65	$200.60
Purchase #7	$8.27	7.377%	$8.8801	$8.88	$8.90	$8.90
7 purchase totals =	$785.22		$844.2754	$844.29	$844.30	$844.30