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	$100.25	9.371%	$109.6444	$109.64	$109.65	$109.60
Purchase #2	$159.48	13.322%	$180.7259	$180.73	$180.75	$180.70
Purchase #3	$240.54	12.281%	$270.0807	$270.08	$270.10	$270.10
Purchase #4	$128.42	7.497%	$138.0476	$138.05	$138.05	$138.00
Purchase #5	$64.84	6.861%	$69.2887	$69.29	$69.30	$69.30
Purchase #6	$70.37	3.145%	$72.5831	$72.58	$72.60	$72.60
Purchase #7	$248.48	6.666%	$265.0437	$265.04	$265.05	$265.00
7 purchase totals =	$1,012.38		$1,105.4141	$1,105.41	$1,105.50	$1,105.30