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	$173.99	4.616%	$182.0214	$182.02	$182.00	$182.00
Purchase #2	$90.40	12.217%	$101.4442	$101.44	$101.45	$101.40
Purchase #3	$222.37	11.273%	$247.4378	$247.44	$247.45	$247.40
Purchase #4	$63.36	5.760%	$67.0095	$67.01	$67.00	$67.00
Purchase #5	$140.45	11.666%	$156.8349	$156.83	$156.85	$156.80
Purchase #6	$215.54	8.432%	$233.7143	$233.71	$233.70	$233.70
Purchase #7	$26.70	8.327%	$28.9233	$28.92	$28.90	$28.90
7 purchase totals =	$932.81		$1,017.3854	$1,017.37	$1,017.35	$1,017.20