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	$104.56	7.273%	$112.1646	$112.16	$112.15	$112.20
Purchase #2	$89.59	11.268%	$99.685	$99.69	$99.70	$99.70
Purchase #3	$246.68	6.346%	$262.3343	$262.33	$262.35	$262.30
Purchase #4	$159.29	10.307%	$175.708	$175.71	$175.70	$175.70
Purchase #5	$171.49	10.798%	$190.0075	$190.01	$190.00	$190.00
Purchase #6	$167.97	10.323%	$185.3095	$185.31	$185.30	$185.30
Purchase #7	$78.26	7.457%	$84.0958	$84.10	$84.10	$84.10
7 purchase totals =	$1,017.84		$1,109.3047	$1,109.31	$1,109.30	$1,109.30