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	$170.86	8.501%	$185.3848	$185.38	$185.40	$185.40
Purchase #2	$155.32	8.266%	$168.1588	$168.16	$168.15	$168.20
Purchase #3	$235.30	7.633%	$253.2604	$253.26	$253.25	$253.30
Purchase #4	$82.88	3.835%	$86.0584	$86.06	$86.05	$86.10
Purchase #5	$115.68	13.738%	$131.5721	$131.57	$131.55	$131.60
Purchase #6	$31.56	6.545%	$33.6256	$33.63	$33.65	$33.60
Purchase #7	$188.83	8.797%	$205.4414	$205.44	$205.45	$205.40
7 purchase totals =	$980.43		$1,063.5015	$1,063.50	$1,063.50	$1,063.60