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	$60.88	10.115%	$67.038	$67.04	$67.05	$67.00
Purchase #2	$55.66	7.506%	$59.8378	$59.84	$59.85	$59.80
Purchase #3	$58.62	11.761%	$65.5143	$65.51	$65.50	$65.50
Purchase #4	$224.99	3.687%	$233.2854	$233.29	$233.30	$233.30
Purchase #5	$10.49	13.127%	$11.867	$11.87	$11.85	$11.90
Purchase #6	$5.96	7.537%	$6.4092	$6.41	$6.40	$6.40
Purchase #7	$219.95	13.366%	$249.3485	$249.35	$249.35	$249.30
7 purchase totals =	$636.55		$693.3002	$693.31	$693.30	$693.20