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	$37.80	10.780%	$41.8748	$41.87	$41.85	$41.90
Purchase #2	$151.51	13.247%	$171.5805	$171.58	$171.60	$171.60
Purchase #3	$17.56	3.736%	$18.216	$18.22	$18.20	$18.20
Purchase #4	$145.51	11.727%	$162.574	$162.57	$162.55	$162.60
Purchase #5	$95.33	3.770%	$98.9239	$98.92	$98.90	$98.90
Purchase #6	$130.57	13.213%	$147.8222	$147.82	$147.80	$147.80
Purchase #7	$95.48	6.501%	$101.6872	$101.69	$101.70	$101.70
7 purchase totals =	$673.76		$742.6786	$742.67	$742.60	$742.70