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	$103.56	5.780%	$109.5458	$109.55	$109.55	$109.50
Purchase #2	$141.54	6.502%	$150.7429	$150.74	$150.75	$150.70
Purchase #3	$86.64	3.373%	$89.5624	$89.56	$89.55	$89.60
Purchase #4	$119.94	12.190%	$134.5607	$134.56	$134.55	$134.60
Purchase #5	$186.73	12.361%	$209.8117	$209.81	$209.80	$209.80
Purchase #6	$33.63	10.315%	$37.0989	$37.10	$37.10	$37.10
Purchase #7	$107.35	7.189%	$115.0674	$115.07	$115.05	$115.10
7 purchase totals =	$779.39		$846.3898	$846.39	$846.35	$846.40