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	$155.87	10.295%	$171.9168	$171.92	$171.90	$171.90
Purchase #2	$48.27	5.731%	$51.0364	$51.04	$51.05	$51.00
Purchase #3	$62.63	4.280%	$65.3106	$65.31	$65.30	$65.30
Purchase #4	$70.46	9.798%	$77.3637	$77.36	$77.35	$77.40
Purchase #5	$213.29	4.817%	$223.5642	$223.56	$223.55	$223.60
Purchase #6	$220.59	13.540%	$250.4579	$250.46	$250.45	$250.50
Purchase #7	$109.49	9.142%	$119.4996	$119.50	$119.50	$119.50
7 purchase totals =	$880.60		$959.1492	$959.15	$959.10	$959.20