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	$52.57	12.204%	$58.9856	$58.99	$59.00	$59.00
Purchase #2	$220.81	13.843%	$251.3767	$251.38	$251.40	$251.40
Purchase #3	$182.77	3.594%	$189.3388	$189.34	$189.35	$189.30
Purchase #4	$112.95	4.597%	$118.1423	$118.14	$118.15	$118.10
Purchase #5	$35.81	8.744%	$38.9412	$38.94	$38.95	$38.90
Purchase #6	$165.53	3.805%	$171.8284	$171.83	$171.85	$171.80
Purchase #7	$188.86	4.107%	$196.6165	$196.62	$196.60	$196.60
7 purchase totals =	$959.30		$1,025.2295	$1,025.24	$1,025.30	$1,025.10