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	$44.86	11.592%	$50.0602	$50.06	$50.05	$50.10
Purchase #2	$83.91	9.506%	$91.8865	$91.89	$91.90	$91.90
Purchase #3	$150.48	10.801%	$166.7333	$166.73	$166.75	$166.70
Purchase #4	$138.95	4.184%	$144.7637	$144.76	$144.75	$144.80
Purchase #5	$73.78	5.815%	$78.0703	$78.07	$78.05	$78.10
Purchase #6	$231.47	4.192%	$241.1732	$241.17	$241.15	$241.20
Purchase #7	$237.95	6.459%	$253.3192	$253.32	$253.30	$253.30
7 purchase totals =	$961.40		$1,026.0064	$1,026.00	$1,025.95	$1,026.10