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	$221.61	9.313%	$242.2485	$242.25	$242.25	$242.20
Purchase #2	$72.56	13.377%	$82.2664	$82.27	$82.25	$82.30
Purchase #3	$47.46	8.635%	$51.5582	$51.56	$51.55	$51.60
Purchase #4	$177.79	4.371%	$185.5612	$185.56	$185.55	$185.60
Purchase #5	$232.93	9.790%	$255.7338	$255.73	$255.75	$255.70
Purchase #6	$57.65	4.516%	$60.2535	$60.25	$60.25	$60.30
Purchase #7	$160.54	13.675%	$182.4938	$182.49	$182.50	$182.50
7 purchase totals =	$970.54		$1,060.1154	$1,060.11	$1,060.10	$1,060.20