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	$183.79	11.362%	$204.6722	$204.67	$204.65	$204.70
Purchase #2	$131.63	10.539%	$145.5025	$145.50	$145.50	$145.50
Purchase #3	$16.37	10.443%	$18.0795	$18.08	$18.10	$18.10
Purchase #4	$201.87	5.790%	$213.5583	$213.56	$213.55	$213.60
Purchase #5	$141.42	12.146%	$158.5969	$158.60	$158.60	$158.60
Purchase #6	$248.31	6.632%	$264.7779	$264.78	$264.80	$264.80
Purchase #7	$76.63	3.146%	$79.0408	$79.04	$79.05	$79.00
7 purchase totals =	$1,000.02		$1,084.2281	$1,084.23	$1,084.25	$1,084.30