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	$248.34	6.655%	$264.867	$264.87	$264.85	$264.90
Purchase #2	$234.34	10.271%	$258.4091	$258.41	$258.40	$258.40
Purchase #3	$246.34	3.829%	$255.7724	$255.77	$255.75	$255.80
Purchase #4	$32.82	7.372%	$35.2395	$35.24	$35.25	$35.20
Purchase #5	$73.93	13.247%	$83.7235	$83.72	$83.70	$83.70
Purchase #6	$174.75	7.188%	$187.311	$187.31	$187.30	$187.30
Purchase #7	$56.34	8.381%	$61.0619	$61.06	$61.05	$61.10
7 purchase totals =	$1,066.86		$1,146.3844	$1,146.38	$1,146.30	$1,146.40