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	$120.36	5.118%	$126.52	$126.52	$126.50	$126.50
Purchase #2	$224.78	11.255%	$250.079	$250.08	$250.10	$250.10
Purchase #3	$148.78	11.723%	$166.2215	$166.22	$166.20	$166.20
Purchase #4	$70.74	12.337%	$79.4672	$79.47	$79.45	$79.50
Purchase #5	$198.37	8.526%	$215.283	$215.28	$215.30	$215.30
Purchase #6	$182.91	4.577%	$191.2818	$191.28	$191.30	$191.30
Purchase #7	$29.78	13.352%	$33.7562	$33.76	$33.75	$33.80
7 purchase totals =	$975.72		$1,062.6087	$1,062.61	$1,062.60	$1,062.70