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	$238.36	5.182%	$250.7118	$250.71	$250.70	$250.70
Purchase #2	$222.67	10.118%	$245.1998	$245.20	$245.20	$245.20
Purchase #3	$36.55	11.314%	$40.6853	$40.69	$40.70	$40.70
Purchase #4	$197.51	6.407%	$210.1645	$210.16	$210.15	$210.20
Purchase #5	$36.90	10.343%	$40.7166	$40.72	$40.70	$40.70
Purchase #6	$181.36	8.193%	$196.2188	$196.22	$196.20	$196.20
Purchase #7	$84.98	9.236%	$92.8288	$92.83	$92.85	$92.80
7 purchase totals =	$998.33		$1,076.5256	$1,076.53	$1,076.50	$1,076.50