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	$79.60	4.681%	$83.3261	$83.33	$83.35	$83.30
Purchase #2	$25.90	6.755%	$27.6495	$27.65	$27.65	$27.60
Purchase #3	$76.96	9.573%	$84.3274	$84.33	$84.35	$84.30
Purchase #4	$155.56	8.119%	$168.1899	$168.19	$168.20	$168.20
Purchase #5	$172.40	10.739%	$190.914	$190.91	$190.90	$190.90
Purchase #6	$91.89	5.168%	$96.6389	$96.64	$96.65	$96.60
Purchase #7	$85.46	5.328%	$90.0133	$90.01	$90.00	$90.00
7 purchase totals =	$687.77		$741.0591	$741.06	$741.10	$740.90