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	$125.52	12.608%	$141.3456	$141.35	$141.35	$141.30
Purchase #2	$98.98	7.433%	$106.3372	$106.34	$106.35	$106.30
Purchase #3	$126.55	12.591%	$142.4839	$142.48	$142.50	$142.50
Purchase #4	$20.62	9.645%	$22.6088	$22.61	$22.60	$22.60
Purchase #5	$187.84	12.834%	$211.9474	$211.95	$211.95	$211.90
Purchase #6	$82.93	7.771%	$89.3745	$89.37	$89.35	$89.40
Purchase #7	$123.29	10.685%	$136.4635	$136.46	$136.45	$136.50
7 purchase totals =	$765.73		$850.5609	$850.56	$850.55	$850.50