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	$145.44	9.544%	$159.3208	$159.32	$159.30	$159.30
Purchase #2	$30.32	11.797%	$33.8969	$33.90	$33.90	$33.90
Purchase #3	$99.80	6.119%	$105.9068	$105.91	$105.90	$105.90
Purchase #4	$90.87	9.860%	$99.8298	$99.83	$99.85	$99.80
Purchase #5	$222.38	8.173%	$240.5551	$240.56	$240.55	$240.60
Purchase #6	$164.46	9.514%	$180.1067	$180.11	$180.10	$180.10
Purchase #7	$135.32	6.226%	$143.745	$143.75	$143.75	$143.70
7 purchase totals =	$888.59		$963.3611	$963.38	$963.35	$963.30