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	$89.37	8.444%	$96.9164	$96.92	$96.90	$96.90
Purchase #2	$145.85	9.742%	$160.0587	$160.06	$160.05	$160.10
Purchase #3	$248.26	6.204%	$263.6621	$263.66	$263.65	$263.70
Purchase #4	$61.61	9.329%	$67.3576	$67.36	$67.35	$67.40
Purchase #5	$34.66	12.185%	$38.8833	$38.88	$38.90	$38.90
Purchase #6	$234.67	4.327%	$244.8242	$244.82	$244.80	$244.80
Purchase #7	$98.50	13.224%	$111.5256	$111.53	$111.55	$111.50
7 purchase totals =	$912.92		$983.2279	$983.23	$983.20	$983.30