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	$5.87	13.704%	$6.6744	$6.67	$6.65	$6.70
Purchase #2	$64.97	11.818%	$72.6482	$72.65	$72.65	$72.60
Purchase #3	$42.28	7.812%	$45.5829	$45.58	$45.60	$45.60
Purchase #4	$218.53	9.218%	$238.6741	$238.67	$238.65	$238.70
Purchase #5	$156.31	3.773%	$162.2076	$162.21	$162.20	$162.20
Purchase #6	$179.86	4.615%	$188.1605	$188.16	$188.15	$188.20
Purchase #7	$207.98	11.146%	$231.1615	$231.16	$231.15	$231.20
7 purchase totals =	$875.80		$945.1092	$945.10	$945.05	$945.20