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	$167.32	11.394%	$186.3844	$186.38	$186.40	$186.40
Purchase #2	$90.34	11.207%	$100.4644	$100.46	$100.45	$100.50
Purchase #3	$90.87	5.723%	$96.0705	$96.07	$96.05	$96.10
Purchase #4	$196.94	6.179%	$209.1089	$209.11	$209.10	$209.10
Purchase #5	$128.45	7.296%	$137.8217	$137.82	$137.80	$137.80
Purchase #6	$206.42	13.148%	$233.5601	$233.56	$233.55	$233.60
Purchase #7	$78.48	7.553%	$84.4076	$84.41	$84.40	$84.40
7 purchase totals =	$958.82		$1,047.8176	$1,047.81	$1,047.75	$1,047.90