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	$97.38	12.807%	$109.8515	$109.85	$109.85	$109.90
Purchase #2	$242.40	3.714%	$251.4027	$251.40	$251.40	$251.40
Purchase #3	$24.77	13.624%	$28.1447	$28.14	$28.15	$28.10
Purchase #4	$153.74	7.687%	$165.558	$165.56	$165.55	$165.60
Purchase #5	$195.41	7.297%	$209.6691	$209.67	$209.65	$209.70
Purchase #6	$241.88	9.741%	$265.4415	$265.44	$265.45	$265.40
Purchase #7	$55.89	5.669%	$59.0584	$59.06	$59.05	$59.10
7 purchase totals =	$1,011.47		$1,089.1259	$1,089.12	$1,089.10	$1,089.20