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	$43.29	7.534%	$46.5515	$46.55	$46.55	$46.60
Purchase #2	$211.44	13.818%	$240.6568	$240.66	$240.65	$240.70
Purchase #3	$50.46	3.108%	$52.0283	$52.03	$52.05	$52.00
Purchase #4	$81.93	4.669%	$85.7553	$85.76	$85.75	$85.80
Purchase #5	$71.35	9.479%	$78.1133	$78.11	$78.10	$78.10
Purchase #6	$243.54	6.412%	$259.1558	$259.16	$259.15	$259.20
Purchase #7	$100.67	12.326%	$113.0786	$113.08	$113.10	$113.10
7 purchase totals =	$802.68		$875.3396	$875.35	$875.35	$875.50