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	$227.92	6.592%	$242.9445	$242.94	$242.95	$242.90
Purchase #2	$67.86	6.859%	$72.5145	$72.51	$72.50	$72.50
Purchase #3	$186.55	12.242%	$209.3875	$209.39	$209.40	$209.40
Purchase #4	$190.67	11.807%	$213.1824	$213.18	$213.20	$213.20
Purchase #5	$164.86	4.499%	$172.2771	$172.28	$172.30	$172.30
Purchase #6	$106.83	5.529%	$112.7366	$112.74	$112.75	$112.70
Purchase #7	$27.87	11.243%	$31.0034	$31.00	$31.00	$31.00
7 purchase totals =	$972.56		$1,054.0460	$1,054.04	$1,054.10	$1,054.00