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	$99.27	4.411%	$103.6488	$103.65	$103.65	$103.60
Purchase #2	$184.32	6.451%	$196.2105	$196.21	$196.20	$196.20
Purchase #3	$31.81	13.365%	$36.0614	$36.06	$36.05	$36.10
Purchase #4	$178.33	6.279%	$189.5273	$189.53	$189.55	$189.50
Purchase #5	$127.53	3.137%	$131.5306	$131.53	$131.55	$131.50
Purchase #6	$165.90	13.215%	$187.8237	$187.82	$187.80	$187.80
Purchase #7	$152.33	13.523%	$172.9296	$172.93	$172.95	$172.90
7 purchase totals =	$939.49		$1,017.7319	$1,017.73	$1,017.75	$1,017.60