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	$170.67	7.487%	$183.4481	$183.45	$183.45	$183.40
Purchase #2	$153.90	9.304%	$168.2189	$168.22	$168.20	$168.20
Purchase #3	$104.59	6.721%	$111.6195	$111.62	$111.60	$111.60
Purchase #4	$70.39	4.294%	$73.4125	$73.41	$73.40	$73.40
Purchase #5	$246.59	9.107%	$269.047	$269.05	$269.05	$269.00
Purchase #6	$82.29	9.272%	$89.9199	$89.92	$89.90	$89.90
Purchase #7	$109.80	6.502%	$116.9392	$116.94	$116.95	$116.90
7 purchase totals =	$938.23		$1,012.6051	$1,012.61	$1,012.55	$1,012.40