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	$167.63	8.160%	$181.3086	$181.31	$181.30	$181.30
Purchase #2	$184.92	5.851%	$195.7397	$195.74	$195.75	$195.70
Purchase #3	$105.78	5.447%	$111.5418	$111.54	$111.55	$111.50
Purchase #4	$188.84	8.861%	$205.5731	$205.57	$205.55	$205.60
Purchase #5	$64.38	4.234%	$67.1058	$67.11	$67.10	$67.10
Purchase #6	$122.94	6.596%	$131.0491	$131.05	$131.05	$131.00
Purchase #7	$48.77	12.497%	$54.8648	$54.86	$54.85	$54.90
7 purchase totals =	$883.26		$947.1829	$947.18	$947.15	$947.10