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	$242.47	5.641%	$256.1477	$256.15	$256.15	$256.10
Purchase #2	$96.84	7.779%	$104.3732	$104.37	$104.35	$104.40
Purchase #3	$158.98	10.243%	$175.2643	$175.26	$175.25	$175.30
Purchase #4	$81.85	5.629%	$86.4573	$86.46	$86.45	$86.50
Purchase #5	$225.89	11.257%	$251.3184	$251.32	$251.30	$251.30
Purchase #6	$237.57	11.275%	$264.356	$264.36	$264.35	$264.40
Purchase #7	$105.50	5.417%	$111.2149	$111.21	$111.20	$111.20
7 purchase totals =	$1,149.10		$1,249.1318	$1,249.13	$1,249.05	$1,249.20