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	$197.30	8.117%	$213.3148	$213.31	$213.30	$213.30
Purchase #2	$168.94	10.834%	$187.243	$187.24	$187.25	$187.20
Purchase #3	$103.63	5.460%	$109.2882	$109.29	$109.30	$109.30
Purchase #4	$146.56	3.550%	$151.7629	$151.76	$151.75	$151.80
Purchase #5	$119.35	7.513%	$128.3168	$128.32	$128.30	$128.30
Purchase #6	$188.83	10.332%	$208.3399	$208.34	$208.35	$208.30
Purchase #7	$77.77	12.839%	$87.7549	$87.75	$87.75	$87.80
7 purchase totals =	$1,002.38		$1,086.0205	$1,086.01	$1,086.00	$1,086.00