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	$127.74	10.629%	$141.3175	$141.32	$141.30	$141.30
Purchase #2	$63.34	6.461%	$67.4324	$67.43	$67.45	$67.40
Purchase #3	$217.81	3.789%	$226.0628	$226.06	$226.05	$226.10
Purchase #4	$246.28	6.441%	$262.1429	$262.14	$262.15	$262.10
Purchase #5	$36.54	3.391%	$37.7791	$37.78	$37.80	$37.80
Purchase #6	$16.91	9.137%	$18.4551	$18.46	$18.45	$18.50
Purchase #7	$162.27	12.637%	$182.7761	$182.78	$182.80	$182.80
7 purchase totals =	$870.89		$935.9659	$935.97	$936.00	$936.00