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	$210.97	8.653%	$229.2252	$229.23	$229.25	$229.20
Purchase #2	$42.27	8.201%	$45.7366	$45.74	$45.75	$45.70
Purchase #3	$85.78	7.218%	$91.9716	$91.97	$91.95	$92.00
Purchase #4	$216.48	13.533%	$245.7762	$245.78	$245.80	$245.80
Purchase #5	$151.42	3.116%	$156.1382	$156.14	$156.15	$156.10
Purchase #6	$82.82	6.435%	$88.1495	$88.15	$88.15	$88.10
Purchase #7	$99.76	3.532%	$103.2835	$103.28	$103.30	$103.30
7 purchase totals =	$889.50		$960.2808	$960.29	$960.35	$960.20