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	$143.72	13.302%	$162.8376	$162.84	$162.85	$162.80
Purchase #2	$30.84	5.841%	$32.6414	$32.64	$32.65	$32.60
Purchase #3	$85.49	13.370%	$96.92	$96.92	$96.90	$96.90
Purchase #4	$156.83	13.646%	$178.231	$178.23	$178.25	$178.20
Purchase #5	$111.89	11.525%	$124.7853	$124.79	$124.80	$124.80
Purchase #6	$88.67	3.372%	$91.66	$91.66	$91.65	$91.70
Purchase #7	$31.41	9.310%	$34.3343	$34.33	$34.35	$34.30
7 purchase totals =	$648.85		$721.4096	$721.41	$721.45	$721.30