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	$200.61	10.539%	$221.7523	$221.75	$221.75	$221.80
Purchase #2	$142.55	3.285%	$147.2328	$147.23	$147.25	$147.20
Purchase #3	$165.72	3.348%	$171.2683	$171.27	$171.25	$171.30
Purchase #4	$73.62	4.651%	$77.0441	$77.04	$77.05	$77.00
Purchase #5	$137.61	10.690%	$152.3205	$152.32	$152.30	$152.30
Purchase #6	$220.72	3.590%	$228.6438	$228.64	$228.65	$228.60
Purchase #7	$6.35	11.599%	$7.0865	$7.09	$7.10	$7.10
7 purchase totals =	$947.18		$1,005.3483	$1,005.34	$1,005.35	$1,005.30