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	$85.97	8.301%	$93.1064	$93.11	$93.10	$93.10
Purchase #2	$248.63	11.268%	$276.6456	$276.65	$276.65	$276.60
Purchase #3	$127.44	3.486%	$131.8826	$131.88	$131.90	$131.90
Purchase #4	$65.48	10.163%	$72.1347	$72.13	$72.15	$72.10
Purchase #5	$140.89	8.243%	$152.5036	$152.50	$152.50	$152.50
Purchase #6	$90.43	4.704%	$94.6838	$94.68	$94.70	$94.70
Purchase #7	$180.27	5.138%	$189.5323	$189.53	$189.55	$189.50
7 purchase totals =	$939.11		$1,010.4890	$1,010.48	$1,010.55	$1,010.40