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	$104.52	7.479%	$112.3371	$112.34	$112.35	$112.30
Purchase #2	$84.91	5.407%	$89.5011	$89.50	$89.50	$89.50
Purchase #3	$243.78	13.666%	$277.095	$277.10	$277.10	$277.10
Purchase #4	$34.45	11.649%	$38.4631	$38.46	$38.45	$38.50
Purchase #5	$163.77	13.216%	$185.4138	$185.41	$185.40	$185.40
Purchase #6	$120.65	4.158%	$125.6666	$125.67	$125.65	$125.70
Purchase #7	$81.66	10.741%	$90.4311	$90.43	$90.45	$90.40
7 purchase totals =	$833.74		$918.9078	$918.91	$918.90	$918.90