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	$163.51	11.721%	$182.675	$182.68	$182.70	$182.70
Purchase #2	$146.73	6.233%	$155.8757	$155.88	$155.90	$155.90
Purchase #3	$163.64	9.576%	$179.3102	$179.31	$179.30	$179.30
Purchase #4	$111.66	6.377%	$118.7806	$118.78	$118.80	$118.80
Purchase #5	$152.80	10.170%	$168.3398	$168.34	$168.35	$168.30
Purchase #6	$65.94	11.754%	$73.6906	$73.69	$73.70	$73.70
Purchase #7	$170.92	6.716%	$182.399	$182.40	$182.40	$182.40
7 purchase totals =	$975.20		$1,061.0709	$1,061.08	$1,061.15	$1,061.10