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	$99.85	9.862%	$109.6972	$109.70	$109.70	$109.70
Purchase #2	$156.66	4.760%	$164.117	$164.12	$164.10	$164.10
Purchase #3	$135.93	5.845%	$143.8751	$143.88	$143.90	$143.90
Purchase #4	$129.29	6.786%	$138.0636	$138.06	$138.05	$138.10
Purchase #5	$184.56	8.621%	$200.4709	$200.47	$200.45	$200.50
Purchase #6	$20.26	5.226%	$21.3188	$21.32	$21.30	$21.30
Purchase #7	$180.73	8.800%	$196.6342	$196.63	$196.65	$196.60
7 purchase totals =	$907.28		$974.1768	$974.18	$974.15	$974.20