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	$213.77	8.193%	$231.2842	$231.28	$231.30	$231.30
Purchase #2	$88.91	9.751%	$97.5796	$97.58	$97.60	$97.60
Purchase #3	$173.86	7.745%	$187.3255	$187.33	$187.35	$187.30
Purchase #4	$104.31	10.602%	$115.3689	$115.37	$115.35	$115.40
Purchase #5	$82.36	8.323%	$89.2148	$89.21	$89.20	$89.20
Purchase #6	$117.47	8.640%	$127.6194	$127.62	$127.60	$127.60
Purchase #7	$227.66	8.718%	$247.5074	$247.51	$247.50	$247.50
7 purchase totals =	$1,008.34		$1,095.8998	$1,095.90	$1,095.90	$1,095.90