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	$185.43	5.582%	$195.7807	$195.78	$195.80	$195.80
Purchase #2	$229.96	6.765%	$245.5168	$245.52	$245.50	$245.50
Purchase #3	$207.62	4.570%	$217.1082	$217.11	$217.10	$217.10
Purchase #4	$156.36	13.845%	$178.008	$178.01	$178.00	$178.00
Purchase #5	$81.96	4.736%	$85.8416	$85.84	$85.85	$85.80
Purchase #6	$137.65	3.396%	$142.3246	$142.32	$142.30	$142.30
Purchase #7	$128.52	8.789%	$139.8156	$139.82	$139.80	$139.80
7 purchase totals =	$1,127.50		$1,204.3955	$1,204.40	$1,204.35	$1,204.30