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	$187.27	5.676%	$197.8994	$197.90	$197.90	$197.90
Purchase #2	$178.93	4.517%	$187.0123	$187.01	$187.00	$187.00
Purchase #3	$104.89	9.210%	$114.5504	$114.55	$114.55	$114.60
Purchase #4	$78.26	10.283%	$86.3075	$86.31	$86.30	$86.30
Purchase #5	$166.39	3.544%	$172.2869	$172.29	$172.30	$172.30
Purchase #6	$74.34	10.821%	$82.3843	$82.38	$82.40	$82.40
Purchase #7	$194.51	6.354%	$206.8692	$206.87	$206.85	$206.90
7 purchase totals =	$984.59		$1,047.3100	$1,047.31	$1,047.30	$1,047.40