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	$164.38	5.489%	$173.4028	$173.40	$173.40	$173.40
Purchase #2	$118.39	3.111%	$122.0731	$122.07	$122.05	$122.10
Purchase #3	$136.82	11.513%	$152.5721	$152.57	$152.55	$152.60
Purchase #4	$174.34	12.529%	$196.1831	$196.18	$196.20	$196.20
Purchase #5	$225.31	8.862%	$245.277	$245.28	$245.30	$245.30
Purchase #6	$183.48	6.307%	$195.0521	$195.05	$195.05	$195.10
Purchase #7	$85.50	5.450%	$90.1598	$90.16	$90.15	$90.20
7 purchase totals =	$1,088.22		$1,174.7200	$1,174.71	$1,174.70	$1,174.90