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	$52.40	3.460%	$54.213	$54.21	$54.20	$54.20
Purchase #2	$182.93	13.489%	$207.6054	$207.61	$207.60	$207.60
Purchase #3	$52.37	13.791%	$59.5923	$59.59	$59.60	$59.60
Purchase #4	$59.93	13.169%	$67.8222	$67.82	$67.80	$67.80
Purchase #5	$22.63	9.742%	$24.8346	$24.83	$24.85	$24.80
Purchase #6	$38.61	4.578%	$40.3776	$40.38	$40.40	$40.40
Purchase #7	$107.26	7.140%	$114.9184	$114.92	$114.90	$114.90
7 purchase totals =	$516.13		$569.3635	$569.36	$569.35	$569.30