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	$53.64	10.634%	$59.3441	$59.34	$59.35	$59.30
Purchase #2	$73.25	3.270%	$75.6453	$75.65	$75.65	$75.60
Purchase #3	$201.37	10.393%	$222.2984	$222.30	$222.30	$222.30
Purchase #4	$134.27	6.843%	$143.4581	$143.46	$143.45	$143.50
Purchase #5	$35.32	10.827%	$39.1441	$39.14	$39.15	$39.10
Purchase #6	$83.63	12.662%	$94.2192	$94.22	$94.20	$94.20
Purchase #7	$69.45	4.153%	$72.3343	$72.33	$72.35	$72.30
7 purchase totals =	$650.93		$706.4435	$706.44	$706.45	$706.30