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	$175.93	6.212%	$186.8588	$186.86	$186.85	$186.90
Purchase #2	$112.52	5.238%	$118.4138	$118.41	$118.40	$118.40
Purchase #3	$25.43	8.561%	$27.6071	$27.61	$27.60	$27.60
Purchase #4	$96.30	5.237%	$101.3432	$101.34	$101.35	$101.30
Purchase #5	$225.75	12.716%	$254.4564	$254.46	$254.45	$254.50
Purchase #6	$117.56	10.420%	$129.8098	$129.81	$129.80	$129.80
Purchase #7	$165.33	11.524%	$184.3826	$184.38	$184.40	$184.40
7 purchase totals =	$918.82		$1,002.8717	$1,002.87	$1,002.85	$1,002.90