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	$6.71	7.716%	$7.2277	$7.23	$7.25	$7.20
Purchase #2	$245.50	6.815%	$262.2308	$262.23	$262.25	$262.20
Purchase #3	$98.70	3.640%	$102.2927	$102.29	$102.30	$102.30
Purchase #4	$248.81	6.619%	$265.2787	$265.28	$265.30	$265.30
Purchase #5	$61.59	8.397%	$66.7617	$66.76	$66.75	$66.80
Purchase #6	$142.64	6.578%	$152.0229	$152.02	$152.00	$152.00
Purchase #7	$215.40	3.294%	$222.4953	$222.50	$222.50	$222.50
7 purchase totals =	$1,019.35		$1,078.3098	$1,078.31	$1,078.35	$1,078.30