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	$194.61	7.270%	$208.7581	$208.76	$208.75	$208.80
Purchase #2	$75.41	8.723%	$81.988	$81.99	$82.00	$82.00
Purchase #3	$114.65	12.348%	$128.807	$128.81	$128.80	$128.80
Purchase #4	$85.60	4.450%	$89.4092	$89.41	$89.40	$89.40
Purchase #5	$184.32	6.361%	$196.0446	$196.04	$196.05	$196.00
Purchase #6	$138.70	12.564%	$156.1263	$156.13	$156.15	$156.10
Purchase #7	$219.77	10.230%	$242.2525	$242.25	$242.25	$242.30
7 purchase totals =	$1,013.06		$1,103.3857	$1,103.39	$1,103.40	$1,103.40