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	$91.47	9.360%	$100.0316	$100.03	$100.05	$100.00
Purchase #2	$188.29	5.280%	$198.2317	$198.23	$198.25	$198.20
Purchase #3	$246.66	6.794%	$263.4181	$263.42	$263.40	$263.40
Purchase #4	$139.60	11.394%	$155.506	$155.51	$155.50	$155.50
Purchase #5	$198.27	7.506%	$213.1521	$213.15	$213.15	$213.20
Purchase #6	$72.40	7.148%	$77.5752	$77.58	$77.60	$77.60
Purchase #7	$97.49	6.140%	$103.4759	$103.48	$103.50	$103.50
7 purchase totals =	$1,034.18		$1,111.3906	$1,111.40	$1,111.45	$1,111.40