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	$157.41	3.456%	$162.8501	$162.85	$162.85	$162.90
Purchase #2	$250.52	12.667%	$282.2534	$282.25	$282.25	$282.30
Purchase #3	$72.39	4.119%	$75.3717	$75.37	$75.35	$75.40
Purchase #4	$234.71	12.429%	$263.8821	$263.88	$263.90	$263.90
Purchase #5	$232.82	11.398%	$259.3568	$259.36	$259.35	$259.40
Purchase #6	$115.72	11.872%	$129.4583	$129.46	$129.45	$129.50
Purchase #7	$115.53	10.680%	$127.8686	$127.87	$127.85	$127.90
7 purchase totals =	$1,179.10		$1,301.0410	$1,301.04	$1,301.00	$1,301.30