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	$94.64	11.666%	$105.6807	$105.68	$105.70	$105.70
Purchase #2	$31.90	11.136%	$35.4524	$35.45	$35.45	$35.50
Purchase #3	$93.30	6.279%	$99.1583	$99.16	$99.15	$99.20
Purchase #4	$53.54	8.282%	$57.9742	$57.97	$57.95	$58.00
Purchase #5	$24.93	9.172%	$27.2166	$27.22	$27.20	$27.20
Purchase #6	$162.35	6.128%	$172.2988	$172.30	$172.30	$172.30
Purchase #7	$120.36	9.203%	$131.4367	$131.44	$131.45	$131.40
7 purchase totals =	$581.02		$629.2177	$629.22	$629.20	$629.30