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	$124.30	6.683%	$132.607	$132.61	$132.60	$132.60
Purchase #2	$133.87	8.250%	$144.9143	$144.91	$144.90	$144.90
Purchase #3	$203.84	8.718%	$221.6108	$221.61	$221.60	$221.60
Purchase #4	$89.38	8.518%	$96.9934	$96.99	$97.00	$97.00
Purchase #5	$44.98	4.123%	$46.8345	$46.83	$46.85	$46.80
Purchase #6	$177.42	7.740%	$191.1523	$191.15	$191.15	$191.20
Purchase #7	$156.74	6.838%	$167.4579	$167.46	$167.45	$167.50
7 purchase totals =	$930.53		$1,001.5702	$1,001.56	$1,001.55	$1,001.60