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	$107.56	3.789%	$111.6354	$111.64	$111.65	$111.60
Purchase #2	$203.73	8.179%	$220.3931	$220.39	$220.40	$220.40
Purchase #3	$217.36	8.821%	$236.5333	$236.53	$236.55	$236.50
Purchase #4	$96.48	13.244%	$109.2578	$109.26	$109.25	$109.30
Purchase #5	$80.43	13.823%	$91.5478	$91.55	$91.55	$91.50
Purchase #6	$153.87	7.370%	$165.2102	$165.21	$165.20	$165.20
Purchase #7	$192.27	12.165%	$215.6596	$215.66	$215.65	$215.70
7 purchase totals =	$1,051.70		$1,150.2372	$1,150.24	$1,150.25	$1,150.20