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	$56.98	8.742%	$61.9612	$61.96	$61.95	$62.00
Purchase #2	$240.91	12.398%	$270.778	$270.78	$270.80	$270.80
Purchase #3	$45.31	6.327%	$48.1768	$48.18	$48.20	$48.20
Purchase #4	$236.89	11.585%	$264.3337	$264.33	$264.35	$264.30
Purchase #5	$64.26	13.426%	$72.8875	$72.89	$72.90	$72.90
Purchase #6	$60.79	9.514%	$66.5736	$66.57	$66.55	$66.60
Purchase #7	$169.36	10.104%	$186.4721	$186.47	$186.45	$186.50
7 purchase totals =	$874.50		$971.1829	$971.18	$971.20	$971.30