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	$198.33	8.740%	$215.664	$215.66	$215.65	$215.70
Purchase #2	$129.53	10.474%	$143.097	$143.10	$143.10	$143.10
Purchase #3	$29.69	5.521%	$31.3292	$31.33	$31.35	$31.30
Purchase #4	$222.41	11.476%	$247.9338	$247.93	$247.95	$247.90
Purchase #5	$64.27	5.354%	$67.711	$67.71	$67.70	$67.70
Purchase #6	$214.29	3.260%	$221.2759	$221.28	$221.30	$221.30
Purchase #7	$125.89	9.201%	$137.4731	$137.47	$137.45	$137.50
7 purchase totals =	$984.41		$1,064.4840	$1,064.48	$1,064.50	$1,064.50