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	$64.42	11.704%	$71.9597	$71.96	$71.95	$72.00
Purchase #2	$11.89	7.503%	$12.7821	$12.78	$12.80	$12.80
Purchase #3	$78.75	5.672%	$83.2167	$83.22	$83.20	$83.20
Purchase #4	$72.73	8.519%	$78.9259	$78.93	$78.95	$78.90
Purchase #5	$91.91	7.666%	$98.9558	$98.96	$98.95	$99.00
Purchase #6	$221.66	10.156%	$244.1718	$244.17	$244.15	$244.20
Purchase #7	$183.38	8.129%	$198.287	$198.29	$198.30	$198.30
7 purchase totals =	$724.74		$788.2990	$788.31	$788.30	$788.40