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	$248.37	7.430%	$266.8239	$266.82	$266.80	$266.80
Purchase #2	$59.46	3.413%	$61.4894	$61.49	$61.50	$61.50
Purchase #3	$29.84	11.543%	$33.2844	$33.28	$33.30	$33.30
Purchase #4	$221.84	5.614%	$234.2941	$234.29	$234.30	$234.30
Purchase #5	$90.30	5.302%	$95.0877	$95.09	$95.10	$95.10
Purchase #6	$127.95	10.680%	$141.6151	$141.62	$141.60	$141.60
Purchase #7	$232.37	12.488%	$261.3884	$261.39	$261.40	$261.40
7 purchase totals =	$1,010.13		$1,093.9830	$1,093.98	$1,094.00	$1,094.00