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	$88.98	3.687%	$92.2607	$92.26	$92.25	$92.30
Purchase #2	$56.66	5.258%	$59.6392	$59.64	$59.65	$59.60
Purchase #3	$34.63	9.116%	$37.7869	$37.79	$37.80	$37.80
Purchase #4	$18.99	8.276%	$20.5616	$20.56	$20.55	$20.60
Purchase #5	$189.30	3.779%	$196.4536	$196.45	$196.45	$196.50
Purchase #6	$123.47	5.635%	$130.4275	$130.43	$130.45	$130.40
Purchase #7	$165.78	12.376%	$186.2969	$186.30	$186.30	$186.30
7 purchase totals =	$677.81		$723.4264	$723.43	$723.45	$723.50