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	$240.44	5.789%	$254.3591	$254.36	$254.35	$254.40
Purchase #2	$94.71	11.846%	$105.9293	$105.93	$105.95	$105.90
Purchase #3	$200.30	7.118%	$214.5574	$214.56	$214.55	$214.60
Purchase #4	$172.69	13.793%	$196.5091	$196.51	$196.50	$196.50
Purchase #5	$217.62	10.410%	$240.2742	$240.27	$240.25	$240.30
Purchase #6	$219.97	10.539%	$243.1526	$243.15	$243.15	$243.20
Purchase #7	$196.43	6.222%	$208.6519	$208.65	$208.65	$208.70
7 purchase totals =	$1,342.16		$1,463.4336	$1,463.43	$1,463.40	$1,463.60