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	$87.44	5.617%	$92.3515	$92.35	$92.35	$92.40
Purchase #2	$76.59	6.551%	$81.6074	$81.61	$81.60	$81.60
Purchase #3	$240.77	10.589%	$266.2651	$266.27	$266.25	$266.30
Purchase #4	$117.56	8.450%	$127.4938	$127.49	$127.50	$127.50
Purchase #5	$84.96	8.833%	$92.4645	$92.46	$92.45	$92.50
Purchase #6	$90.40	8.863%	$98.4122	$98.41	$98.40	$98.40
Purchase #7	$181.59	8.348%	$196.7491	$196.75	$196.75	$196.70
7 purchase totals =	$879.31		$955.3436	$955.34	$955.30	$955.40