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	$175.84	11.640%	$196.3078	$196.31	$196.30	$196.30
Purchase #2	$145.89	4.116%	$151.8948	$151.89	$151.90	$151.90
Purchase #3	$109.29	11.777%	$122.1611	$122.16	$122.15	$122.20
Purchase #4	$57.63	4.520%	$60.2349	$60.23	$60.25	$60.20
Purchase #5	$129.56	12.582%	$145.8612	$145.86	$145.85	$145.90
Purchase #6	$184.88	6.487%	$196.8732	$196.87	$196.85	$196.90
Purchase #7	$204.66	6.528%	$218.0202	$218.02	$218.00	$218.00
7 purchase totals =	$1,007.75		$1,091.3532	$1,091.34	$1,091.30	$1,091.40