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	$142.71	7.816%	$153.8642	$153.86	$153.85	$153.90
Purchase #2	$98.91	6.644%	$105.4816	$105.48	$105.50	$105.50
Purchase #3	$49.79	13.118%	$56.3215	$56.32	$56.30	$56.30
Purchase #4	$59.43	12.758%	$67.0121	$67.01	$67.00	$67.00
Purchase #5	$235.26	4.353%	$245.5009	$245.50	$245.50	$245.50
Purchase #6	$166.44	3.507%	$172.2771	$172.28	$172.30	$172.30
Purchase #7	$63.35	3.131%	$65.3335	$65.33	$65.35	$65.30
7 purchase totals =	$815.89		$865.7909	$865.78	$865.80	$865.80