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	$40.49	11.420%	$45.114	$45.11	$45.10	$45.10
Purchase #2	$198.39	7.145%	$212.565	$212.57	$212.55	$212.60
Purchase #3	$178.82	4.585%	$187.0189	$187.02	$187.00	$187.00
Purchase #4	$164.43	11.830%	$183.8821	$183.88	$183.90	$183.90
Purchase #5	$231.57	3.143%	$238.8482	$238.85	$238.85	$238.80
Purchase #6	$220.33	13.846%	$250.8369	$250.84	$250.85	$250.80
Purchase #7	$77.79	11.339%	$86.6106	$86.61	$86.60	$86.60
7 purchase totals =	$1,111.82		$1,204.8757	$1,204.88	$1,204.85	$1,204.80