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	$52.95	8.374%	$57.384	$57.38	$57.40	$57.40
Purchase #2	$195.46	13.716%	$222.2693	$222.27	$222.25	$222.30
Purchase #3	$48.47	5.435%	$51.1043	$51.10	$51.10	$51.10
Purchase #4	$28.69	11.108%	$31.8769	$31.88	$31.90	$31.90
Purchase #5	$157.47	8.654%	$171.0975	$171.10	$171.10	$171.10
Purchase #6	$241.49	13.114%	$273.159	$273.16	$273.15	$273.20
Purchase #7	$128.86	9.587%	$141.2138	$141.21	$141.20	$141.20
7 purchase totals =	$853.39		$948.1048	$948.10	$948.10	$948.20