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	$179.76	10.227%	$198.1441	$198.14	$198.15	$198.10
Purchase #2	$123.33	3.703%	$127.8969	$127.90	$127.90	$127.90
Purchase #3	$144.46	8.496%	$156.7333	$156.73	$156.75	$156.70
Purchase #4	$136.86	4.716%	$143.3143	$143.31	$143.30	$143.30
Purchase #5	$69.88	13.245%	$79.1356	$79.14	$79.15	$79.10
Purchase #6	$80.26	11.670%	$89.6263	$89.63	$89.65	$89.60
Purchase #7	$195.26	9.773%	$214.3428	$214.34	$214.35	$214.30
7 purchase totals =	$929.81		$1,009.1933	$1,009.19	$1,009.25	$1,009.00