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	$193.33	7.167%	$207.186	$207.19	$207.20	$207.20
Purchase #2	$96.94	11.297%	$107.8913	$107.89	$107.90	$107.90
Purchase #3	$70.73	10.717%	$78.3101	$78.31	$78.30	$78.30
Purchase #4	$109.87	9.493%	$120.3	$120.30	$120.30	$120.30
Purchase #5	$73.49	7.406%	$78.9327	$78.93	$78.95	$78.90
Purchase #6	$86.41	3.827%	$89.7169	$89.72	$89.70	$89.70
Purchase #7	$240.88	8.190%	$260.6081	$260.61	$260.60	$260.60
7 purchase totals =	$871.65		$942.9451	$942.95	$942.95	$942.90