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	$225.76	8.279%	$244.4507	$244.45	$244.45	$244.50
Purchase #2	$126.47	11.439%	$140.9369	$140.94	$140.95	$140.90
Purchase #3	$53.57	6.277%	$56.9326	$56.93	$56.95	$56.90
Purchase #4	$191.93	4.294%	$200.1715	$200.17	$200.15	$200.20
Purchase #5	$101.25	8.284%	$109.6376	$109.64	$109.65	$109.60
Purchase #6	$229.86	3.699%	$238.3625	$238.36	$238.35	$238.40
Purchase #7	$151.88	9.849%	$166.8387	$166.84	$166.85	$166.80
7 purchase totals =	$1,080.72		$1,157.3305	$1,157.33	$1,157.35	$1,157.30