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	$162.77	4.613%	$170.2786	$170.28	$170.30	$170.30
Purchase #2	$7.29	6.125%	$7.7365	$7.74	$7.75	$7.70
Purchase #3	$171.76	11.601%	$191.6859	$191.69	$191.70	$191.70
Purchase #4	$183.35	4.635%	$191.8483	$191.85	$191.85	$191.80
Purchase #5	$39.56	6.128%	$41.9842	$41.98	$42.00	$42.00
Purchase #6	$123.85	12.802%	$139.7053	$139.71	$139.70	$139.70
Purchase #7	$136.98	3.109%	$141.2387	$141.24	$141.25	$141.20
7 purchase totals =	$825.56		$884.4775	$884.49	$884.55	$884.40