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	$165.91	12.695%	$186.9723	$186.97	$186.95	$187.00
Purchase #2	$190.52	13.526%	$216.2897	$216.29	$216.30	$216.30
Purchase #3	$181.29	3.736%	$188.063	$188.06	$188.05	$188.10
Purchase #4	$41.54	8.747%	$45.1735	$45.17	$45.15	$45.20
Purchase #5	$89.70	9.541%	$98.2583	$98.26	$98.25	$98.30
Purchase #6	$41.96	7.754%	$45.2136	$45.21	$45.20	$45.20
Purchase #7	$51.36	6.513%	$54.7051	$54.71	$54.70	$54.70
7 purchase totals =	$762.28		$834.6755	$834.67	$834.60	$834.80