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	$229.48	9.803%	$251.9759	$251.98	$252.00	$252.00
Purchase #2	$205.92	8.443%	$223.3058	$223.31	$223.30	$223.30
Purchase #3	$179.65	4.628%	$187.9642	$187.96	$187.95	$188.00
Purchase #4	$84.48	7.477%	$90.7966	$90.80	$90.80	$90.80
Purchase #5	$97.30	8.341%	$105.4158	$105.42	$105.40	$105.40
Purchase #6	$126.75	11.260%	$141.0221	$141.02	$141.00	$141.00
Purchase #7	$45.83	3.578%	$47.4698	$47.47	$47.45	$47.50
7 purchase totals =	$969.41		$1,047.9502	$1,047.96	$1,047.90	$1,048.00