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	$105.35	4.127%	$109.6978	$109.70	$109.70	$109.70
Purchase #2	$249.46	6.117%	$264.7195	$264.72	$264.70	$264.70
Purchase #3	$206.95	10.239%	$228.1396	$228.14	$228.15	$228.10
Purchase #4	$189.78	11.661%	$211.9102	$211.91	$211.90	$211.90
Purchase #5	$248.48	3.391%	$256.906	$256.91	$256.90	$256.90
Purchase #6	$68.33	5.782%	$72.2808	$72.28	$72.30	$72.30
Purchase #7	$92.29	11.152%	$102.5822	$102.58	$102.60	$102.60
7 purchase totals =	$1,160.64		$1,246.2361	$1,246.24	$1,246.25	$1,246.20