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	$205.87	13.289%	$233.2281	$233.23	$233.25	$233.20
Purchase #2	$36.61	12.451%	$41.1683	$41.17	$41.15	$41.20
Purchase #3	$102.83	7.608%	$110.6533	$110.65	$110.65	$110.70
Purchase #4	$78.83	9.372%	$86.2179	$86.22	$86.20	$86.20
Purchase #5	$96.51	3.487%	$99.8753	$99.88	$99.90	$99.90
Purchase #6	$57.33	10.767%	$63.5027	$63.50	$63.50	$63.50
Purchase #7	$144.39	12.132%	$161.9074	$161.91	$161.90	$161.90
7 purchase totals =	$722.37		$796.5530	$796.56	$796.55	$796.60