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	$79.77	7.651%	$85.8732	$85.87	$85.85	$85.90
Purchase #2	$61.82	9.367%	$67.6107	$67.61	$67.60	$67.60
Purchase #3	$158.96	12.437%	$178.7299	$178.73	$178.75	$178.70
Purchase #4	$69.50	10.833%	$77.0289	$77.03	$77.05	$77.00
Purchase #5	$63.98	12.809%	$72.1752	$72.18	$72.20	$72.20
Purchase #6	$70.70	11.563%	$78.875	$78.88	$78.90	$78.90
Purchase #7	$131.99	11.791%	$147.5529	$147.55	$147.55	$147.60
7 purchase totals =	$636.72		$707.8458	$707.85	$707.90	$707.90