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	$197.81	12.781%	$223.0921	$223.09	$223.10	$223.10
Purchase #2	$228.65	3.693%	$237.094	$237.09	$237.10	$237.10
Purchase #3	$109.50	7.682%	$117.9118	$117.91	$117.90	$117.90
Purchase #4	$79.92	13.174%	$90.4487	$90.45	$90.45	$90.40
Purchase #5	$64.57	11.599%	$72.0595	$72.06	$72.05	$72.10
Purchase #6	$166.44	12.810%	$187.761	$187.76	$187.75	$187.80
Purchase #7	$94.81	6.662%	$101.1262	$101.13	$101.15	$101.10
7 purchase totals =	$941.70		$1,029.4933	$1,029.49	$1,029.50	$1,029.50