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	$115.40	13.395%	$130.8578	$130.86	$130.85	$130.90
Purchase #2	$43.86	4.223%	$45.7122	$45.71	$45.70	$45.70
Purchase #3	$78.73	9.464%	$86.181	$86.18	$86.20	$86.20
Purchase #4	$8.48	11.847%	$9.4846	$9.48	$9.50	$9.50
Purchase #5	$34.90	8.227%	$37.7712	$37.77	$37.75	$37.80
Purchase #6	$80.74	13.302%	$91.48	$91.48	$91.50	$91.50
Purchase #7	$85.69	12.298%	$96.2282	$96.23	$96.25	$96.20
7 purchase totals =	$447.80		$497.7150	$497.71	$497.75	$497.80