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	$201.79	5.148%	$212.1781	$212.18	$212.20	$212.20
Purchase #2	$205.75	5.123%	$216.2906	$216.29	$216.30	$216.30
Purchase #3	$56.54	8.242%	$61.2	$61.20	$61.20	$61.20
Purchase #4	$110.31	7.366%	$118.4354	$118.44	$118.45	$118.40
Purchase #5	$89.67	11.441%	$99.9291	$99.93	$99.95	$99.90
Purchase #6	$100.65	9.196%	$109.9058	$109.91	$109.90	$109.90
Purchase #7	$138.43	13.292%	$156.8301	$156.83	$156.85	$156.80
7 purchase totals =	$903.14		$974.7691	$974.78	$974.85	$974.70