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	$53.66	10.151%	$59.107	$59.11	$59.10	$59.10
Purchase #2	$79.34	12.296%	$89.0956	$89.10	$89.10	$89.10
Purchase #3	$230.90	13.185%	$261.3442	$261.34	$261.35	$261.30
Purchase #4	$217.54	4.343%	$226.9878	$226.99	$227.00	$227.00
Purchase #5	$81.54	4.629%	$85.3145	$85.31	$85.30	$85.30
Purchase #6	$250.48	5.597%	$264.4994	$264.50	$264.50	$264.50
Purchase #7	$141.99	13.193%	$160.7227	$160.72	$160.70	$160.70
7 purchase totals =	$1,055.45		$1,147.0712	$1,147.07	$1,147.05	$1,147.00