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	$95.97	12.671%	$108.1304	$108.13	$108.15	$108.10
Purchase #2	$141.62	10.551%	$156.5623	$156.56	$156.55	$156.60
Purchase #3	$31.97	10.721%	$35.3975	$35.40	$35.40	$35.40
Purchase #4	$60.32	6.294%	$64.1165	$64.12	$64.10	$64.10
Purchase #5	$30.93	5.342%	$32.5823	$32.58	$32.60	$32.60
Purchase #6	$92.85	13.279%	$105.1796	$105.18	$105.20	$105.20
Purchase #7	$232.94	13.486%	$264.3543	$264.35	$264.35	$264.40
7 purchase totals =	$686.60		$766.3229	$766.32	$766.35	$766.40