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	$151.78	5.449%	$160.0505	$160.05	$160.05	$160.10
Purchase #2	$27.47	4.273%	$28.6438	$28.64	$28.65	$28.60
Purchase #3	$33.81	11.222%	$37.6042	$37.60	$37.60	$37.60
Purchase #4	$168.69	8.412%	$182.8802	$182.88	$182.90	$182.90
Purchase #5	$97.96	7.487%	$105.2943	$105.29	$105.30	$105.30
Purchase #6	$172.58	6.315%	$183.4784	$183.48	$183.50	$183.50
Purchase #7	$128.92	12.762%	$145.3728	$145.37	$145.35	$145.40
7 purchase totals =	$781.21		$843.3242	$843.31	$843.35	$843.40