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	$33.85	5.607%	$35.748	$35.75	$35.75	$35.70
Purchase #2	$159.54	6.152%	$169.3549	$169.35	$169.35	$169.40
Purchase #3	$246.96	13.735%	$280.88	$280.88	$280.90	$280.90
Purchase #4	$28.26	9.829%	$31.0377	$31.04	$31.05	$31.00
Purchase #5	$16.63	9.320%	$18.1799	$18.18	$18.20	$18.20
Purchase #6	$73.42	6.817%	$78.425	$78.43	$78.45	$78.40
Purchase #7	$164.34	5.773%	$173.8273	$173.83	$173.85	$173.80
7 purchase totals =	$723.00		$787.4528	$787.46	$787.55	$787.40