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	$172.75	10.788%	$191.3863	$191.39	$191.40	$191.40
Purchase #2	$135.53	4.393%	$141.4838	$141.48	$141.50	$141.50
Purchase #3	$84.73	6.809%	$90.4993	$90.50	$90.50	$90.50
Purchase #4	$157.92	9.276%	$172.5687	$172.57	$172.55	$172.60
Purchase #5	$226.50	4.352%	$236.3573	$236.36	$236.35	$236.40
Purchase #6	$162.86	7.779%	$175.5289	$175.53	$175.55	$175.50
Purchase #7	$182.27	8.654%	$198.0436	$198.04	$198.05	$198.00
7 purchase totals =	$1,122.56		$1,205.8679	$1,205.87	$1,205.90	$1,205.90