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	$148.58	11.566%	$165.7648	$165.76	$165.75	$165.80
Purchase #2	$108.59	5.536%	$114.6015	$114.60	$114.60	$114.60
Purchase #3	$241.28	7.440%	$259.2312	$259.23	$259.25	$259.20
Purchase #4	$185.38	3.328%	$191.5494	$191.55	$191.55	$191.50
Purchase #5	$99.60	9.740%	$109.301	$109.30	$109.30	$109.30
Purchase #6	$102.38	4.417%	$106.9021	$106.90	$106.90	$106.90
Purchase #7	$151.82	12.333%	$170.544	$170.54	$170.55	$170.50
7 purchase totals =	$1,037.63		$1,117.8940	$1,117.88	$1,117.90	$1,117.80