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	$215.87	3.253%	$222.8923	$222.89	$222.90	$222.90
Purchase #2	$47.81	13.695%	$54.3576	$54.36	$54.35	$54.40
Purchase #3	$220.72	7.387%	$237.0246	$237.02	$237.00	$237.00
Purchase #4	$191.58	10.435%	$211.5714	$211.57	$211.55	$211.60
Purchase #5	$89.98	7.362%	$96.6043	$96.60	$96.60	$96.60
Purchase #6	$18.54	3.325%	$19.1565	$19.16	$19.15	$19.20
Purchase #7	$42.39	10.620%	$46.8918	$46.89	$46.90	$46.90
7 purchase totals =	$826.89		$888.4985	$888.49	$888.45	$888.60