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	$172.88	7.802%	$186.3681	$186.37	$186.35	$186.40
Purchase #2	$88.58	8.561%	$96.1633	$96.16	$96.15	$96.20
Purchase #3	$103.76	5.130%	$109.0829	$109.08	$109.10	$109.10
Purchase #4	$150.80	3.861%	$156.6224	$156.62	$156.60	$156.60
Purchase #5	$205.80	9.452%	$225.2522	$225.25	$225.25	$225.30
Purchase #6	$67.68	8.721%	$73.5824	$73.58	$73.60	$73.60
Purchase #7	$212.41	3.460%	$219.7594	$219.76	$219.75	$219.80
7 purchase totals =	$1,001.91		$1,066.8307	$1,066.82	$1,066.80	$1,067.00