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	$165.49	9.222%	$180.7515	$180.75	$180.75	$180.80
Purchase #2	$226.95	6.146%	$240.8983	$240.90	$240.90	$240.90
Purchase #3	$174.39	5.259%	$183.5612	$183.56	$183.55	$183.60
Purchase #4	$118.94	3.494%	$123.0958	$123.10	$123.10	$123.10
Purchase #5	$169.49	8.831%	$184.4577	$184.46	$184.45	$184.50
Purchase #6	$99.76	6.172%	$105.9172	$105.92	$105.90	$105.90
Purchase #7	$222.31	5.858%	$235.3329	$235.33	$235.35	$235.30
7 purchase totals =	$1,177.33		$1,254.0146	$1,254.02	$1,254.00	$1,254.10