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	$186.53	10.271%	$205.6885	$205.69	$205.70	$205.70
Purchase #2	$37.58	11.451%	$41.8833	$41.88	$41.90	$41.90
Purchase #3	$150.97	5.866%	$159.8259	$159.83	$159.85	$159.80
Purchase #4	$48.69	13.188%	$55.1112	$55.11	$55.10	$55.10
Purchase #5	$40.99	3.615%	$42.4718	$42.47	$42.45	$42.50
Purchase #6	$92.56	4.111%	$96.3651	$96.37	$96.35	$96.40
Purchase #7	$183.94	10.650%	$203.5296	$203.53	$203.55	$203.50
7 purchase totals =	$741.26		$804.8754	$804.88	$804.90	$804.90