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	$169.38	9.781%	$185.9471	$185.95	$185.95	$185.90
Purchase #2	$180.64	9.474%	$197.7538	$197.75	$197.75	$197.80
Purchase #3	$100.42	3.513%	$103.9478	$103.95	$103.95	$103.90
Purchase #4	$244.36	11.860%	$273.3411	$273.34	$273.35	$273.30
Purchase #5	$68.53	5.740%	$72.4636	$72.46	$72.45	$72.50
Purchase #6	$133.52	4.207%	$139.1372	$139.14	$139.15	$139.10
Purchase #7	$30.51	8.264%	$33.0313	$33.03	$33.05	$33.00
7 purchase totals =	$927.36		$1,005.6219	$1,005.62	$1,005.65	$1,005.50