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	$156.48	11.703%	$174.7929	$174.79	$174.80	$174.80
Purchase #2	$214.63	4.108%	$223.447	$223.45	$223.45	$223.40
Purchase #3	$145.64	12.734%	$164.1858	$164.19	$164.20	$164.20
Purchase #4	$166.33	5.383%	$175.2835	$175.28	$175.30	$175.30
Purchase #5	$83.38	13.114%	$94.3145	$94.31	$94.30	$94.30
Purchase #6	$156.79	10.240%	$172.8453	$172.85	$172.85	$172.80
Purchase #7	$128.43	10.670%	$142.1335	$142.13	$142.15	$142.10
7 purchase totals =	$1,051.68		$1,147.0025	$1,147.00	$1,147.05	$1,146.90