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	$60.74	7.107%	$65.0568	$65.06	$65.05	$65.10
Purchase #2	$25.94	11.164%	$28.8359	$28.84	$28.85	$28.80
Purchase #3	$98.28	4.212%	$102.4196	$102.42	$102.40	$102.40
Purchase #4	$54.32	9.204%	$59.3196	$59.32	$59.30	$59.30
Purchase #5	$220.51	3.655%	$228.5696	$228.57	$228.55	$228.60
Purchase #6	$109.70	12.799%	$123.7405	$123.74	$123.75	$123.70
Purchase #7	$65.64	12.463%	$73.8207	$73.82	$73.80	$73.80
7 purchase totals =	$635.13		$681.7627	$681.77	$681.70	$681.70