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	$72.36	11.163%	$80.4375	$80.44	$80.45	$80.40
Purchase #2	$218.63	3.108%	$225.425	$225.43	$225.45	$225.40
Purchase #3	$185.51	13.599%	$210.7375	$210.74	$210.75	$210.70
Purchase #4	$72.79	7.579%	$78.3068	$78.31	$78.30	$78.30
Purchase #5	$150.36	13.808%	$171.1217	$171.12	$171.10	$171.10
Purchase #6	$121.72	12.274%	$136.6599	$136.66	$136.65	$136.70
Purchase #7	$123.49	12.772%	$139.2621	$139.26	$139.25	$139.30
7 purchase totals =	$944.86		$1,041.9505	$1,041.96	$1,041.95	$1,041.90