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	$91.62	5.703%	$96.8451	$96.85	$96.85	$96.80
Purchase #2	$140.35	11.555%	$156.5674	$156.57	$156.55	$156.60
Purchase #3	$118.54	7.356%	$127.2598	$127.26	$127.25	$127.30
Purchase #4	$239.47	9.588%	$262.4304	$262.43	$262.45	$262.40
Purchase #5	$133.43	7.474%	$143.4026	$143.40	$143.40	$143.40
Purchase #6	$12.82	4.818%	$13.4377	$13.44	$13.45	$13.40
Purchase #7	$249.39	7.612%	$268.3736	$268.37	$268.35	$268.40
7 purchase totals =	$985.62		$1,068.3166	$1,068.32	$1,068.30	$1,068.30