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	$211.95	10.343%	$233.872	$233.87	$233.85	$233.90
Purchase #2	$43.47	12.762%	$49.0176	$49.02	$49.00	$49.00
Purchase #3	$60.30	8.445%	$65.3923	$65.39	$65.40	$65.40
Purchase #4	$218.74	13.783%	$248.8889	$248.89	$248.90	$248.90
Purchase #5	$87.75	11.549%	$97.8842	$97.88	$97.90	$97.90
Purchase #6	$92.47	8.862%	$100.6647	$100.66	$100.65	$100.70
Purchase #7	$93.61	11.452%	$104.3302	$104.33	$104.35	$104.30
7 purchase totals =	$808.29		$900.0499	$900.04	$900.05	$900.10