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	$154.50	6.639%	$164.7573	$164.76	$164.75	$164.80
Purchase #2	$12.94	3.580%	$13.4033	$13.40	$13.40	$13.40
Purchase #3	$200.52	11.370%	$223.3191	$223.32	$223.30	$223.30
Purchase #4	$54.72	4.197%	$57.0166	$57.02	$57.00	$57.00
Purchase #5	$9.53	11.550%	$10.6307	$10.63	$10.65	$10.60
Purchase #6	$76.53	8.303%	$82.8843	$82.88	$82.90	$82.90
Purchase #7	$224.27	9.295%	$245.1159	$245.12	$245.10	$245.10
7 purchase totals =	$733.01		$797.1272	$797.13	$797.10	$797.10