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	$160.71	6.454%	$171.0822	$171.08	$171.10	$171.10
Purchase #2	$29.66	11.700%	$33.1302	$33.13	$33.15	$33.10
Purchase #3	$199.54	10.646%	$220.783	$220.78	$220.80	$220.80
Purchase #4	$58.33	4.698%	$61.0703	$61.07	$61.05	$61.10
Purchase #5	$169.60	12.728%	$191.1867	$191.19	$191.20	$191.20
Purchase #6	$164.95	8.406%	$178.8157	$178.82	$178.80	$178.80
Purchase #7	$149.30	4.730%	$156.3619	$156.36	$156.35	$156.40
7 purchase totals =	$932.09		$1,012.4300	$1,012.43	$1,012.45	$1,012.50