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	$207.52	10.157%	$228.5978	$228.60	$228.60	$228.60
Purchase #2	$114.92	11.230%	$127.8255	$127.83	$127.85	$127.80
Purchase #3	$194.94	8.417%	$211.3481	$211.35	$211.35	$211.30
Purchase #4	$5.80	9.663%	$6.3605	$6.36	$6.35	$6.40
Purchase #5	$182.43	3.123%	$188.1273	$188.13	$188.15	$188.10
Purchase #6	$174.41	6.819%	$186.303	$186.30	$186.30	$186.30
Purchase #7	$50.51	8.485%	$54.7958	$54.80	$54.80	$54.80
7 purchase totals =	$930.53		$1,003.3580	$1,003.37	$1,003.40	$1,003.30