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	$231.43	4.405%	$241.6245	$241.62	$241.60	$241.60
Purchase #2	$31.73	11.562%	$35.3986	$35.40	$35.40	$35.40
Purchase #3	$57.72	7.374%	$61.9763	$61.98	$62.00	$62.00
Purchase #4	$173.28	12.284%	$194.5657	$194.57	$194.55	$194.60
Purchase #5	$163.26	5.262%	$171.8507	$171.85	$171.85	$171.90
Purchase #6	$160.27	5.134%	$168.4983	$168.50	$168.50	$168.50
Purchase #7	$176.26	12.801%	$198.823	$198.82	$198.80	$198.80
7 purchase totals =	$993.95		$1,072.7371	$1,072.74	$1,072.70	$1,072.80