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	$104.36	9.548%	$114.3243	$114.32	$114.30	$114.30
Purchase #2	$156.95	7.662%	$168.9755	$168.98	$169.00	$169.00
Purchase #3	$79.70	3.395%	$82.4058	$82.41	$82.40	$82.40
Purchase #4	$135.72	6.800%	$144.949	$144.95	$144.95	$144.90
Purchase #5	$79.32	8.721%	$86.2375	$86.24	$86.25	$86.20
Purchase #6	$125.31	12.814%	$141.3672	$141.37	$141.35	$141.40
Purchase #7	$18.79	6.751%	$20.0585	$20.06	$20.05	$20.10
7 purchase totals =	$700.15		$758.3178	$758.33	$758.30	$758.30