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	$63.83	12.190%	$71.6109	$71.61	$71.60	$71.60
Purchase #2	$137.88	13.792%	$156.8964	$156.90	$156.90	$156.90
Purchase #3	$123.47	5.222%	$129.9176	$129.92	$129.90	$129.90
Purchase #4	$151.30	11.665%	$168.9491	$168.95	$168.95	$168.90
Purchase #5	$86.66	5.727%	$91.623	$91.62	$91.60	$91.60
Purchase #6	$79.99	11.223%	$88.9673	$88.97	$88.95	$89.00
Purchase #7	$64.52	10.396%	$71.2275	$71.23	$71.25	$71.20
7 purchase totals =	$707.65		$779.1918	$779.20	$779.15	$779.10