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	$183.97	6.760%	$196.4064	$196.41	$196.40	$196.40
Purchase #2	$137.37	4.259%	$143.2206	$143.22	$143.20	$143.20
Purchase #3	$85.73	8.187%	$92.7487	$92.75	$92.75	$92.70
Purchase #4	$150.47	13.460%	$170.7233	$170.72	$170.70	$170.70
Purchase #5	$95.42	5.766%	$100.9219	$100.92	$100.90	$100.90
Purchase #6	$199.96	11.505%	$222.9654	$222.97	$222.95	$223.00
Purchase #7	$238.75	8.608%	$259.3016	$259.30	$259.30	$259.30
7 purchase totals =	$1,091.67		$1,186.2879	$1,186.29	$1,186.20	$1,186.20