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	$147.27	3.578%	$152.5393	$152.54	$152.55	$152.50
Purchase #2	$85.38	13.286%	$96.7236	$96.72	$96.70	$96.70
Purchase #3	$54.42	13.866%	$61.9659	$61.97	$61.95	$62.00
Purchase #4	$206.58	8.277%	$223.6786	$223.68	$223.70	$223.70
Purchase #5	$179.44	9.229%	$196.0005	$196.00	$196.00	$196.00
Purchase #6	$27.63	3.721%	$28.6581	$28.66	$28.65	$28.70
Purchase #7	$196.45	13.845%	$223.6485	$223.65	$223.65	$223.60
7 purchase totals =	$897.17		$983.2145	$983.22	$983.20	$983.20