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	$211.98	10.277%	$233.7652	$233.77	$233.75	$233.80
Purchase #2	$42.72	6.177%	$45.3588	$45.36	$45.35	$45.40
Purchase #3	$142.88	9.830%	$156.9251	$156.93	$156.95	$156.90
Purchase #4	$114.57	11.633%	$127.8979	$127.90	$127.90	$127.90
Purchase #5	$52.83	5.538%	$55.7557	$55.76	$55.75	$55.80
Purchase #6	$142.31	7.816%	$153.4329	$153.43	$153.45	$153.40
Purchase #7	$57.52	4.856%	$60.3132	$60.31	$60.30	$60.30
7 purchase totals =	$764.81		$833.4488	$833.46	$833.45	$833.50