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	$240.95	11.651%	$269.0231	$269.02	$269.00	$269.00
Purchase #2	$35.98	12.111%	$40.3375	$40.34	$40.35	$40.30
Purchase #3	$195.34	8.355%	$211.6607	$211.66	$211.65	$211.70
Purchase #4	$123.63	8.229%	$133.8035	$133.80	$133.80	$133.80
Purchase #5	$173.31	10.406%	$191.3446	$191.34	$191.35	$191.30
Purchase #6	$165.34	13.223%	$187.2029	$187.20	$187.20	$187.20
Purchase #7	$134.51	13.419%	$152.5599	$152.56	$152.55	$152.60
7 purchase totals =	$1,069.06		$1,185.9322	$1,185.92	$1,185.90	$1,185.90