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	$184.92	6.405%	$196.7641	$196.76	$196.75	$196.80
Purchase #2	$194.38	5.413%	$204.9018	$204.90	$204.90	$204.90
Purchase #3	$176.27	4.370%	$183.973	$183.97	$183.95	$184.00
Purchase #4	$6.82	11.174%	$7.5821	$7.58	$7.60	$7.60
Purchase #5	$237.63	3.425%	$245.7688	$245.77	$245.75	$245.80
Purchase #6	$127.63	13.505%	$144.8664	$144.87	$144.85	$144.90
Purchase #7	$164.73	10.189%	$181.5143	$181.51	$181.50	$181.50
7 purchase totals =	$1,092.38		$1,165.3705	$1,165.36	$1,165.30	$1,165.50