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	$30.69	7.403%	$32.962	$32.96	$32.95	$33.00
Purchase #2	$87.61	3.746%	$90.8919	$90.89	$90.90	$90.90
Purchase #3	$245.66	5.848%	$260.0262	$260.03	$260.05	$260.00
Purchase #4	$170.73	9.789%	$187.4428	$187.44	$187.45	$187.40
Purchase #5	$27.28	8.540%	$29.6097	$29.61	$29.60	$29.60
Purchase #6	$207.30	4.469%	$216.5642	$216.56	$216.55	$216.60
Purchase #7	$181.41	3.234%	$187.2768	$187.28	$187.30	$187.30
7 purchase totals =	$950.68		$1,004.7736	$1,004.77	$1,004.80	$1,004.80