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	$180.53	4.650%	$188.9246	$188.92	$188.90	$188.90
Purchase #2	$169.46	3.721%	$175.7656	$175.77	$175.75	$175.80
Purchase #3	$178.51	12.477%	$200.7827	$200.78	$200.80	$200.80
Purchase #4	$27.83	11.664%	$31.0761	$31.08	$31.10	$31.10
Purchase #5	$243.63	4.785%	$255.2877	$255.29	$255.30	$255.30
Purchase #6	$166.86	11.822%	$186.5862	$186.59	$186.60	$186.60
Purchase #7	$53.41	5.418%	$56.3038	$56.30	$56.30	$56.30
7 purchase totals =	$1,020.23		$1,094.7267	$1,094.73	$1,094.75	$1,094.80