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	$131.38	5.102%	$138.083	$138.08	$138.10	$138.10
Purchase #2	$242.90	12.401%	$273.022	$273.02	$273.00	$273.00
Purchase #3	$162.91	5.203%	$171.3862	$171.39	$171.40	$171.40
Purchase #4	$158.68	4.555%	$165.9079	$165.91	$165.90	$165.90
Purchase #5	$141.90	5.764%	$150.0791	$150.08	$150.10	$150.10
Purchase #6	$56.31	8.635%	$61.1724	$61.17	$61.15	$61.20
Purchase #7	$146.58	5.826%	$155.1198	$155.12	$155.10	$155.10
7 purchase totals =	$1,040.66		$1,114.7704	$1,114.77	$1,114.75	$1,114.80