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	$241.28	5.536%	$254.6373	$254.64	$254.65	$254.60
Purchase #2	$92.35	7.504%	$99.2799	$99.28	$99.30	$99.30
Purchase #3	$73.61	12.639%	$82.9136	$82.91	$82.90	$82.90
Purchase #4	$20.39	6.595%	$21.7347	$21.73	$21.75	$21.70
Purchase #5	$194.76	7.443%	$209.256	$209.26	$209.25	$209.30
Purchase #6	$162.45	7.400%	$174.4713	$174.47	$174.45	$174.50
Purchase #7	$46.50	8.194%	$50.3102	$50.31	$50.30	$50.30
7 purchase totals =	$831.34		$892.6030	$892.60	$892.60	$892.60