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	$188.55	3.654%	$195.4396	$195.44	$195.45	$195.40
Purchase #2	$18.46	4.172%	$19.2302	$19.23	$19.25	$19.20
Purchase #3	$238.75	7.151%	$255.823	$255.82	$255.80	$255.80
Purchase #4	$159.27	12.842%	$179.7235	$179.72	$179.70	$179.70
Purchase #5	$26.92	3.630%	$27.8972	$27.90	$27.90	$27.90
Purchase #6	$161.88	5.302%	$170.4629	$170.46	$170.45	$170.50
Purchase #7	$75.62	13.524%	$85.8468	$85.85	$85.85	$85.80
7 purchase totals =	$869.45		$934.4232	$934.42	$934.40	$934.30