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	$123.46	5.651%	$130.4367	$130.44	$130.45	$130.40
Purchase #2	$103.34	8.402%	$112.0226	$112.02	$112.00	$112.00
Purchase #3	$65.77	8.572%	$71.4078	$71.41	$71.40	$71.40
Purchase #4	$69.25	12.872%	$78.1639	$78.16	$78.15	$78.20
Purchase #5	$38.91	9.367%	$42.5547	$42.55	$42.55	$42.60
Purchase #6	$72.43	11.534%	$80.7841	$80.78	$80.80	$80.80
Purchase #7	$153.31	8.316%	$166.0593	$166.06	$166.05	$166.10
7 purchase totals =	$626.47		$681.4291	$681.42	$681.40	$681.50