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	$174.42	12.736%	$196.6341	$196.63	$196.65	$196.60
Purchase #2	$80.36	7.819%	$86.6433	$86.64	$86.65	$86.60
Purchase #3	$127.91	13.742%	$145.4874	$145.49	$145.50	$145.50
Purchase #4	$119.63	9.623%	$131.142	$131.14	$131.15	$131.10
Purchase #5	$48.80	8.459%	$52.928	$52.93	$52.95	$52.90
Purchase #6	$168.33	4.398%	$175.7332	$175.73	$175.75	$175.70
Purchase #7	$96.47	6.651%	$102.8862	$102.89	$102.90	$102.90
7 purchase totals =	$815.92		$891.4542	$891.45	$891.55	$891.30