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	$232.71	9.375%	$254.5266	$254.53	$254.55	$254.50
Purchase #2	$83.42	9.554%	$91.3899	$91.39	$91.40	$91.40
Purchase #3	$83.98	7.426%	$90.2164	$90.22	$90.20	$90.20
Purchase #4	$169.43	6.181%	$179.9025	$179.90	$179.90	$179.90
Purchase #5	$234.49	6.626%	$250.0273	$250.03	$250.05	$250.00
Purchase #6	$211.92	13.407%	$240.3321	$240.33	$240.35	$240.30
Purchase #7	$249.77	4.647%	$261.3768	$261.38	$261.40	$261.40
7 purchase totals =	$1,265.72		$1,367.7716	$1,367.78	$1,367.85	$1,367.70