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	$133.42	13.799%	$151.8306	$151.83	$151.85	$151.80
Purchase #2	$211.56	10.511%	$233.7971	$233.80	$233.80	$233.80
Purchase #3	$187.46	4.229%	$195.3877	$195.39	$195.40	$195.40
Purchase #4	$222.91	3.131%	$229.8893	$229.89	$229.90	$229.90
Purchase #5	$152.98	8.307%	$165.688	$165.69	$165.70	$165.70
Purchase #6	$120.76	11.140%	$134.2127	$134.21	$134.20	$134.20
Purchase #7	$27.75	3.856%	$28.82	$28.82	$28.80	$28.80
7 purchase totals =	$1,056.84		$1,139.6254	$1,139.63	$1,139.65	$1,139.60