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	$59.55	3.260%	$61.4913	$61.49	$61.50	$61.50
Purchase #2	$99.57	6.809%	$106.3497	$106.35	$106.35	$106.30
Purchase #3	$56.68	10.380%	$62.5634	$62.56	$62.55	$62.60
Purchase #4	$49.56	12.149%	$55.581	$55.58	$55.60	$55.60
Purchase #5	$64.91	10.666%	$71.8333	$71.83	$71.85	$71.80
Purchase #6	$174.49	4.514%	$182.3665	$182.37	$182.35	$182.40
Purchase #7	$230.33	5.159%	$242.2127	$242.21	$242.20	$242.20
7 purchase totals =	$735.09		$782.3979	$782.39	$782.40	$782.40