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	$99.32	12.625%	$111.8592	$111.86	$111.85	$111.90
Purchase #2	$224.38	6.272%	$238.4531	$238.45	$238.45	$238.50
Purchase #3	$200.89	12.427%	$225.8546	$225.85	$225.85	$225.90
Purchase #4	$91.30	6.746%	$97.4591	$97.46	$97.45	$97.50
Purchase #5	$155.57	4.607%	$162.7371	$162.74	$162.75	$162.70
Purchase #6	$157.92	11.480%	$176.0492	$176.05	$176.05	$176.00
Purchase #7	$166.53	12.557%	$187.4412	$187.44	$187.45	$187.40
7 purchase totals =	$1,095.91		$1,199.8535	$1,199.85	$1,199.85	$1,199.90