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	$69.36	6.371%	$73.7789	$73.78	$73.80	$73.80
Purchase #2	$250.38	13.693%	$284.6645	$284.66	$284.65	$284.70
Purchase #3	$104.42	4.821%	$109.4541	$109.45	$109.45	$109.50
Purchase #4	$100.75	3.668%	$104.4455	$104.45	$104.45	$104.40
Purchase #5	$147.30	3.373%	$152.2684	$152.27	$152.25	$152.30
Purchase #6	$147.47	10.123%	$162.3984	$162.40	$162.40	$162.40
Purchase #7	$204.33	6.818%	$218.2612	$218.26	$218.25	$218.30
7 purchase totals =	$1,024.01		$1,105.2710	$1,105.27	$1,105.25	$1,105.40