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	$219.30	4.114%	$228.322	$228.32	$228.30	$228.30
Purchase #2	$136.54	9.214%	$149.1208	$149.12	$149.10	$149.10
Purchase #3	$213.56	7.141%	$228.8103	$228.81	$228.80	$228.80
Purchase #4	$28.89	9.212%	$31.5513	$31.55	$31.55	$31.60
Purchase #5	$148.75	12.874%	$167.9001	$167.90	$167.90	$167.90
Purchase #6	$9.83	9.383%	$10.7523	$10.75	$10.75	$10.80
Purchase #7	$116.52	9.758%	$127.89	$127.89	$127.90	$127.90
7 purchase totals =	$873.39		$944.3468	$944.34	$944.30	$944.40