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	$126.32	13.139%	$142.9172	$142.92	$142.90	$142.90
Purchase #2	$165.63	12.764%	$186.771	$186.77	$186.75	$186.80
Purchase #3	$50.91	8.375%	$55.1737	$55.17	$55.15	$55.20
Purchase #4	$133.56	5.405%	$140.7789	$140.78	$140.80	$140.80
Purchase #5	$210.35	11.138%	$233.7788	$233.78	$233.80	$233.80
Purchase #6	$214.39	6.154%	$227.5836	$227.58	$227.60	$227.60
Purchase #7	$64.91	10.797%	$71.9183	$71.92	$71.90	$71.90
7 purchase totals =	$966.07		$1,058.9215	$1,058.92	$1,058.90	$1,059.00