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	$92.66	11.309%	$103.1389	$103.14	$103.15	$103.10
Purchase #2	$178.49	5.411%	$188.1481	$188.15	$188.15	$188.10
Purchase #3	$80.50	13.614%	$91.4593	$91.46	$91.45	$91.50
Purchase #4	$151.64	5.141%	$159.4358	$159.44	$159.45	$159.40
Purchase #5	$181.53	3.529%	$187.9362	$187.94	$187.95	$187.90
Purchase #6	$116.28	6.440%	$123.7684	$123.77	$123.75	$123.80
Purchase #7	$46.26	10.298%	$51.0239	$51.02	$51.00	$51.00
7 purchase totals =	$847.36		$904.9106	$904.92	$904.90	$904.80