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	$50.57	3.648%	$52.4148	$52.41	$52.40	$52.40
Purchase #2	$198.59	6.699%	$211.8935	$211.89	$211.90	$211.90
Purchase #3	$246.46	3.746%	$255.6924	$255.69	$255.70	$255.70
Purchase #4	$76.84	10.121%	$84.617	$84.62	$84.60	$84.60
Purchase #5	$151.44	8.717%	$164.641	$164.64	$164.65	$164.60
Purchase #6	$41.50	11.534%	$46.2866	$46.29	$46.30	$46.30
Purchase #7	$200.74	7.113%	$215.0186	$215.02	$215.00	$215.00
7 purchase totals =	$966.14		$1,030.5639	$1,030.56	$1,030.55	$1,030.50