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	$52.63	8.741%	$57.2304	$57.23	$57.25	$57.20
Purchase #2	$100.29	7.814%	$108.1267	$108.13	$108.15	$108.10
Purchase #3	$79.55	5.769%	$84.1392	$84.14	$84.15	$84.10
Purchase #4	$70.33	10.746%	$77.8877	$77.89	$77.90	$77.90
Purchase #5	$104.30	13.298%	$118.1698	$118.17	$118.15	$118.20
Purchase #6	$94.49	6.741%	$100.8596	$100.86	$100.85	$100.90
Purchase #7	$19.46	4.811%	$20.3962	$20.40	$20.40	$20.40
7 purchase totals =	$521.05		$566.8096	$566.82	$566.85	$566.80