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	$52.82	10.278%	$58.2488	$58.25	$58.25	$58.20
Purchase #2	$106.80	5.514%	$112.689	$112.69	$112.70	$112.70
Purchase #3	$231.64	10.215%	$255.302	$255.30	$255.30	$255.30
Purchase #4	$72.47	6.383%	$77.0958	$77.10	$77.10	$77.10
Purchase #5	$9.98	11.568%	$11.1345	$11.13	$11.15	$11.10
Purchase #6	$45.51	13.767%	$51.7754	$51.78	$51.80	$51.80
Purchase #7	$170.34	8.790%	$185.3129	$185.31	$185.30	$185.30
7 purchase totals =	$689.56		$751.5584	$751.56	$751.60	$751.50