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	$183.51	11.870%	$205.2926	$205.29	$205.30	$205.30
Purchase #2	$182.56	7.582%	$196.4017	$196.40	$196.40	$196.40
Purchase #3	$99.42	5.583%	$104.9706	$104.97	$104.95	$105.00
Purchase #4	$92.83	6.459%	$98.8259	$98.83	$98.85	$98.80
Purchase #5	$144.61	8.409%	$156.7703	$156.77	$156.75	$156.80
Purchase #6	$175.76	10.502%	$194.2183	$194.22	$194.20	$194.20
Purchase #7	$158.34	10.424%	$174.8454	$174.85	$174.85	$174.80
7 purchase totals =	$1,037.03		$1,131.3248	$1,131.33	$1,131.30	$1,131.30