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	$141.44	3.421%	$146.2787	$146.28	$146.30	$146.30
Purchase #2	$166.39	5.346%	$175.2852	$175.29	$175.30	$175.30
Purchase #3	$56.55	8.435%	$61.32	$61.32	$61.30	$61.30
Purchase #4	$99.56	9.620%	$109.1377	$109.14	$109.15	$109.10
Purchase #5	$97.58	10.750%	$108.0699	$108.07	$108.05	$108.10
Purchase #6	$168.86	3.523%	$174.8089	$174.81	$174.80	$174.80
Purchase #7	$45.84	13.400%	$51.9826	$51.98	$52.00	$52.00
7 purchase totals =	$776.22		$826.8830	$826.89	$826.90	$826.90