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	$145.47	3.150%	$150.0523	$150.05	$150.05	$150.10
Purchase #2	$162.63	5.820%	$172.0951	$172.10	$172.10	$172.10
Purchase #3	$173.99	4.861%	$182.4477	$182.45	$182.45	$182.40
Purchase #4	$123.41	13.242%	$139.752	$139.75	$139.75	$139.80
Purchase #5	$145.90	7.140%	$156.3173	$156.32	$156.30	$156.30
Purchase #6	$18.52	11.413%	$20.6337	$20.63	$20.65	$20.60
Purchase #7	$249.74	5.134%	$262.5617	$262.56	$262.55	$262.60
7 purchase totals =	$1,019.66		$1,083.8598	$1,083.86	$1,083.85	$1,083.90