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	$69.31	3.852%	$71.9798	$71.98	$72.00	$72.00
Purchase #2	$248.40	10.863%	$275.3837	$275.38	$275.40	$275.40
Purchase #3	$211.54	6.230%	$224.7189	$224.72	$224.70	$224.70
Purchase #4	$184.99	3.691%	$191.818	$191.82	$191.80	$191.80
Purchase #5	$103.34	3.658%	$107.1202	$107.12	$107.10	$107.10
Purchase #6	$127.52	12.851%	$143.9076	$143.91	$143.90	$143.90
Purchase #7	$215.69	11.331%	$240.1298	$240.13	$240.15	$240.10
7 purchase totals =	$1,160.79		$1,255.0580	$1,255.06	$1,255.05	$1,255.00