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	$83.89	12.569%	$94.4341	$94.43	$94.45	$94.40
Purchase #2	$249.90	7.577%	$268.8349	$268.83	$268.85	$268.80
Purchase #3	$220.73	12.629%	$248.606	$248.61	$248.60	$248.60
Purchase #4	$86.63	3.228%	$89.4264	$89.43	$89.45	$89.40
Purchase #5	$160.86	5.850%	$170.2703	$170.27	$170.25	$170.30
Purchase #6	$78.95	5.323%	$83.1525	$83.15	$83.15	$83.20
Purchase #7	$60.88	10.374%	$67.1957	$67.20	$67.20	$67.20
7 purchase totals =	$941.84		$1,021.9199	$1,021.92	$1,021.95	$1,021.90