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	$169.86	9.236%	$185.5483	$185.55	$185.55	$185.50
Purchase #2	$109.38	8.660%	$118.8523	$118.85	$118.85	$118.90
Purchase #3	$224.63	8.765%	$244.3188	$244.32	$244.30	$244.30
Purchase #4	$118.75	7.142%	$127.2311	$127.23	$127.25	$127.20
Purchase #5	$247.77	4.699%	$259.4127	$259.41	$259.40	$259.40
Purchase #6	$213.45	13.746%	$242.7908	$242.79	$242.80	$242.80
Purchase #7	$239.41	4.824%	$250.9591	$250.96	$250.95	$251.00
7 purchase totals =	$1,323.25		$1,429.1131	$1,429.11	$1,429.10	$1,429.10