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	$179.29	6.296%	$190.5781	$190.58	$190.60	$190.60
Purchase #2	$194.56	6.133%	$206.4924	$206.49	$206.50	$206.50
Purchase #3	$35.33	11.312%	$39.3265	$39.33	$39.35	$39.30
Purchase #4	$227.80	11.705%	$254.464	$254.46	$254.45	$254.50
Purchase #5	$232.85	9.513%	$255.001	$255.00	$255.00	$255.00
Purchase #6	$68.45	6.524%	$72.9157	$72.92	$72.90	$72.90
Purchase #7	$22.60	11.867%	$25.2819	$25.28	$25.30	$25.30
7 purchase totals =	$960.88		$1,044.0596	$1,044.06	$1,044.10	$1,044.10