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	$161.43	7.103%	$172.8964	$172.90	$172.90	$172.90
Purchase #2	$165.25	11.132%	$183.6456	$183.65	$183.65	$183.60
Purchase #3	$229.33	3.418%	$237.1685	$237.17	$237.15	$237.20
Purchase #4	$53.56	3.511%	$55.4405	$55.44	$55.45	$55.40
Purchase #5	$140.39	5.670%	$148.3501	$148.35	$148.35	$148.40
Purchase #6	$198.27	13.615%	$225.2645	$225.26	$225.25	$225.30
Purchase #7	$142.59	9.637%	$156.3314	$156.33	$156.35	$156.30
7 purchase totals =	$1,090.82		$1,179.0970	$1,179.10	$1,179.10	$1,179.10