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	$140.73	7.331%	$151.0469	$151.05	$151.05	$151.00
Purchase #2	$146.57	3.750%	$152.0664	$152.07	$152.05	$152.10
Purchase #3	$174.51	4.333%	$182.0715	$182.07	$182.05	$182.10
Purchase #4	$94.41	11.316%	$105.0934	$105.09	$105.10	$105.10
Purchase #5	$88.77	3.338%	$91.7331	$91.73	$91.75	$91.70
Purchase #6	$59.30	3.826%	$61.5688	$61.57	$61.55	$61.60
Purchase #7	$135.55	4.275%	$141.3448	$141.34	$141.35	$141.30
7 purchase totals =	$839.84		$884.9249	$884.92	$884.90	$884.90