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	$166.87	5.515%	$176.0729	$176.07	$176.05	$176.10
Purchase #2	$223.70	6.476%	$238.1868	$238.19	$238.20	$238.20
Purchase #3	$174.34	4.324%	$181.8785	$181.88	$181.90	$181.90
Purchase #4	$9.57	10.501%	$10.5749	$10.57	$10.55	$10.60
Purchase #5	$210.89	5.618%	$222.7378	$222.74	$222.75	$222.70
Purchase #6	$80.48	12.141%	$90.2511	$90.25	$90.25	$90.30
Purchase #7	$229.50	4.699%	$240.2842	$240.28	$240.30	$240.30
7 purchase totals =	$1,095.35		$1,159.9862	$1,159.98	$1,160.00	$1,160.10