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	$248.71	4.440%	$259.7527	$259.75	$259.75	$259.80
Purchase #2	$85.50	10.247%	$94.2612	$94.26	$94.25	$94.30
Purchase #3	$80.30	3.230%	$82.8937	$82.89	$82.90	$82.90
Purchase #4	$165.35	6.506%	$176.1077	$176.11	$176.10	$176.10
Purchase #5	$247.39	6.718%	$264.0097	$264.01	$264.00	$264.00
Purchase #6	$152.70	6.403%	$162.4774	$162.48	$162.50	$162.50
Purchase #7	$208.52	3.160%	$215.1092	$215.11	$215.10	$215.10
7 purchase totals =	$1,188.47		$1,254.6116	$1,254.61	$1,254.60	$1,254.70