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	$236.61	11.671%	$264.2248	$264.22	$264.20	$264.20
Purchase #2	$90.67	11.316%	$100.9302	$100.93	$100.95	$100.90
Purchase #3	$29.90	4.212%	$31.1594	$31.16	$31.15	$31.20
Purchase #4	$14.48	4.332%	$15.1073	$15.11	$15.10	$15.10
Purchase #5	$185.78	7.860%	$200.3823	$200.38	$200.40	$200.40
Purchase #6	$188.38	4.853%	$197.5221	$197.52	$197.50	$197.50
Purchase #7	$249.84	6.818%	$266.8741	$266.87	$266.85	$266.90
7 purchase totals =	$995.66		$1,076.2002	$1,076.19	$1,076.15	$1,076.20