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	$53.60	12.837%	$60.4806	$60.48	$60.50	$60.50
Purchase #2	$229.78	5.759%	$243.013	$243.01	$243.00	$243.00
Purchase #3	$86.42	8.807%	$94.031	$94.03	$94.05	$94.00
Purchase #4	$158.32	10.257%	$174.5589	$174.56	$174.55	$174.60
Purchase #5	$250.30	3.736%	$259.6512	$259.65	$259.65	$259.70
Purchase #6	$117.34	11.692%	$131.0594	$131.06	$131.05	$131.10
Purchase #7	$117.98	11.541%	$131.5961	$131.60	$131.60	$131.60
7 purchase totals =	$1,013.74		$1,094.3902	$1,094.39	$1,094.40	$1,094.50