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	$201.42	9.253%	$220.0574	$220.06	$220.05	$220.10
Purchase #2	$20.89	9.654%	$22.9067	$22.91	$22.90	$22.90
Purchase #3	$70.60	10.651%	$78.1196	$78.12	$78.10	$78.10
Purchase #4	$55.30	8.302%	$59.891	$59.89	$59.90	$59.90
Purchase #5	$85.35	7.235%	$91.5251	$91.53	$91.55	$91.50
Purchase #6	$62.56	4.529%	$65.3933	$65.39	$65.40	$65.40
Purchase #7	$63.61	12.395%	$71.4945	$71.49	$71.50	$71.50
7 purchase totals =	$559.73		$609.3876	$609.39	$609.40	$609.40