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	$239.41	3.599%	$248.0264	$248.03	$248.05	$248.00
Purchase #2	$77.40	4.687%	$81.0277	$81.03	$81.05	$81.00
Purchase #3	$100.48	3.354%	$103.8501	$103.85	$103.85	$103.90
Purchase #4	$104.25	6.344%	$110.8636	$110.86	$110.85	$110.90
Purchase #5	$165.55	4.698%	$173.3275	$173.33	$173.35	$173.30
Purchase #6	$167.37	13.625%	$190.1742	$190.17	$190.15	$190.20
Purchase #7	$166.90	7.503%	$179.4225	$179.42	$179.40	$179.40
7 purchase totals =	$1,021.36		$1,086.6920	$1,086.69	$1,086.70	$1,086.70