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	$129.97	11.816%	$145.3273	$145.33	$145.35	$145.30
Purchase #2	$94.87	3.436%	$98.1297	$98.13	$98.15	$98.10
Purchase #3	$225.67	13.818%	$256.8531	$256.85	$256.85	$256.90
Purchase #4	$98.87	13.753%	$112.4676	$112.47	$112.45	$112.50
Purchase #5	$177.78	9.199%	$194.134	$194.13	$194.15	$194.10
Purchase #6	$77.61	13.630%	$88.1882	$88.19	$88.20	$88.20
Purchase #7	$136.55	10.428%	$150.7894	$150.79	$150.80	$150.80
7 purchase totals =	$941.32		$1,045.8893	$1,045.89	$1,045.95	$1,045.90