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	$78.44	11.596%	$87.5359	$87.54	$87.55	$87.50
Purchase #2	$98.36	8.222%	$106.4472	$106.45	$106.45	$106.40
Purchase #3	$80.97	9.190%	$88.4111	$88.41	$88.40	$88.40
Purchase #4	$60.32	12.492%	$67.8552	$67.86	$67.85	$67.90
Purchase #5	$198.75	5.463%	$209.6077	$209.61	$209.60	$209.60
Purchase #6	$101.81	4.432%	$106.3222	$106.32	$106.30	$106.30
Purchase #7	$86.34	5.243%	$90.8668	$90.87	$90.85	$90.90
7 purchase totals =	$704.99		$757.0461	$757.06	$757.00	$757.00