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	$209.86	11.422%	$233.8302	$233.83	$233.85	$233.80
Purchase #2	$48.67	3.372%	$50.3112	$50.31	$50.30	$50.30
Purchase #3	$9.75	6.465%	$10.3803	$10.38	$10.40	$10.40
Purchase #4	$99.46	6.588%	$106.0124	$106.01	$106.00	$106.00
Purchase #5	$159.38	3.672%	$165.2324	$165.23	$165.25	$165.20
Purchase #6	$72.98	13.367%	$82.7352	$82.74	$82.75	$82.70
Purchase #7	$224.96	3.301%	$232.3859	$232.39	$232.40	$232.40
7 purchase totals =	$825.06		$880.8876	$880.89	$880.95	$880.80