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	$42.62	9.549%	$46.6898	$46.69	$46.70	$46.70
Purchase #2	$101.79	12.275%	$114.2847	$114.28	$114.30	$114.30
Purchase #3	$248.80	13.734%	$282.9702	$282.97	$282.95	$283.00
Purchase #4	$101.33	8.193%	$109.632	$109.63	$109.65	$109.60
Purchase #5	$175.30	5.245%	$184.4945	$184.49	$184.50	$184.50
Purchase #6	$85.27	11.478%	$95.0573	$95.06	$95.05	$95.10
Purchase #7	$73.36	11.809%	$82.0231	$82.02	$82.00	$82.00
7 purchase totals =	$828.47		$915.1516	$915.14	$915.15	$915.20