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	$65.63	7.776%	$70.7334	$70.73	$70.75	$70.70
Purchase #2	$218.79	3.319%	$226.0516	$226.05	$226.05	$226.10
Purchase #3	$74.63	4.836%	$78.2391	$78.24	$78.25	$78.20
Purchase #4	$164.41	6.118%	$174.4686	$174.47	$174.45	$174.50
Purchase #5	$48.98	5.805%	$51.8233	$51.82	$51.80	$51.80
Purchase #6	$124.55	5.417%	$131.2969	$131.30	$131.30	$131.30
Purchase #7	$89.86	10.679%	$99.4561	$99.46	$99.45	$99.50
7 purchase totals =	$786.85		$832.0690	$832.07	$832.05	$832.10