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	$151.96	8.110%	$164.284	$164.28	$164.30	$164.30
Purchase #2	$26.28	9.304%	$28.7251	$28.73	$28.75	$28.70
Purchase #3	$145.96	9.231%	$159.4336	$159.43	$159.45	$159.40
Purchase #4	$136.88	4.378%	$142.8726	$142.87	$142.85	$142.90
Purchase #5	$215.37	3.458%	$222.8175	$222.82	$222.80	$222.80
Purchase #6	$91.96	5.630%	$97.1373	$97.14	$97.15	$97.10
Purchase #7	$197.79	13.178%	$223.8548	$223.85	$223.85	$223.90
7 purchase totals =	$966.20		$1,039.1249	$1,039.12	$1,039.15	$1,039.10