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	$188.92	4.111%	$196.6865	$196.69	$196.70	$196.70
Purchase #2	$116.75	3.551%	$120.8958	$120.90	$120.90	$120.90
Purchase #3	$195.49	11.452%	$217.8775	$217.88	$217.90	$217.90
Purchase #4	$190.93	13.778%	$217.2363	$217.24	$217.25	$217.20
Purchase #5	$62.93	10.391%	$69.4691	$69.47	$69.45	$69.50
Purchase #6	$114.74	10.794%	$127.125	$127.13	$127.15	$127.10
Purchase #7	$129.89	9.347%	$142.0308	$142.03	$142.05	$142.00
7 purchase totals =	$999.65		$1,091.3210	$1,091.34	$1,091.40	$1,091.30