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	$69.66	4.563%	$72.8386	$72.84	$72.85	$72.80
Purchase #2	$80.39	5.326%	$84.6716	$84.67	$84.65	$84.70
Purchase #3	$40.40	4.549%	$42.2378	$42.24	$42.25	$42.20
Purchase #4	$222.43	11.872%	$248.8369	$248.84	$248.85	$248.80
Purchase #5	$165.77	13.765%	$188.5882	$188.59	$188.60	$188.60
Purchase #6	$155.37	8.592%	$168.7194	$168.72	$168.70	$168.70
Purchase #7	$81.93	11.611%	$91.4429	$91.44	$91.45	$91.40
7 purchase totals =	$815.95		$897.3354	$897.34	$897.35	$897.20