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	$68.48	4.195%	$71.3527	$71.35	$71.35	$71.40
Purchase #2	$186.31	10.587%	$206.0346	$206.03	$206.05	$206.00
Purchase #3	$96.86	5.642%	$102.3248	$102.32	$102.30	$102.30
Purchase #4	$84.37	7.191%	$90.437	$90.44	$90.45	$90.40
Purchase #5	$173.88	4.520%	$181.7394	$181.74	$181.75	$181.70
Purchase #6	$122.92	3.589%	$127.3316	$127.33	$127.35	$127.30
Purchase #7	$63.86	6.136%	$67.7784	$67.78	$67.80	$67.80
7 purchase totals =	$796.68		$846.9985	$846.99	$847.05	$846.90