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	$38.91	7.275%	$41.7407	$41.74	$41.75	$41.70
Purchase #2	$90.88	5.297%	$95.6939	$95.69	$95.70	$95.70
Purchase #3	$49.78	13.351%	$56.4261	$56.43	$56.45	$56.40
Purchase #4	$96.82	9.771%	$106.2803	$106.28	$106.30	$106.30
Purchase #5	$238.58	10.710%	$264.1319	$264.13	$264.15	$264.10
Purchase #6	$108.80	10.502%	$120.2262	$120.23	$120.25	$120.20
Purchase #7	$162.86	5.538%	$171.8792	$171.88	$171.90	$171.90
7 purchase totals =	$786.63		$856.3783	$856.38	$856.50	$856.30