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	$43.62	7.168%	$46.7467	$46.75	$46.75	$46.70
Purchase #2	$48.29	8.155%	$52.228	$52.23	$52.25	$52.20
Purchase #3	$186.26	9.467%	$203.8932	$203.89	$203.90	$203.90
Purchase #4	$102.36	10.794%	$113.4087	$113.41	$113.40	$113.40
Purchase #5	$92.94	6.765%	$99.2274	$99.23	$99.25	$99.20
Purchase #6	$174.64	12.427%	$196.3425	$196.34	$196.35	$196.30
Purchase #7	$37.72	4.249%	$39.3227	$39.32	$39.30	$39.30
7 purchase totals =	$685.83		$751.1692	$751.17	$751.20	$751.00