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	$88.43	3.702%	$91.7037	$91.70	$91.70	$91.70
Purchase #2	$126.96	3.613%	$131.5471	$131.55	$131.55	$131.50
Purchase #3	$43.47	7.611%	$46.7785	$46.78	$46.80	$46.80
Purchase #4	$234.55	13.837%	$267.0047	$267.00	$267.00	$267.00
Purchase #5	$243.48	3.371%	$251.6877	$251.69	$251.70	$251.70
Purchase #6	$82.56	9.167%	$90.1283	$90.13	$90.15	$90.10
Purchase #7	$162.50	10.463%	$179.5024	$179.50	$179.50	$179.50
7 purchase totals =	$981.95		$1,058.3524	$1,058.35	$1,058.40	$1,058.30