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	$118.86	8.211%	$128.6196	$128.62	$128.60	$128.60
Purchase #2	$173.59	9.111%	$189.4058	$189.41	$189.40	$189.40
Purchase #3	$138.93	11.855%	$155.4002	$155.40	$155.40	$155.40
Purchase #4	$89.46	11.158%	$99.4419	$99.44	$99.45	$99.40
Purchase #5	$150.34	3.280%	$155.2712	$155.27	$155.25	$155.30
Purchase #6	$76.45	13.659%	$86.8923	$86.89	$86.90	$86.90
Purchase #7	$212.86	10.530%	$235.2742	$235.27	$235.25	$235.30
7 purchase totals =	$960.49		$1,050.3052	$1,050.30	$1,050.25	$1,050.30