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	$104.70	9.739%	$114.8967	$114.90	$114.90	$114.90
Purchase #2	$245.79	6.720%	$262.3071	$262.31	$262.30	$262.30
Purchase #3	$124.37	3.103%	$128.2292	$128.23	$128.25	$128.20
Purchase #4	$159.72	13.729%	$181.648	$181.65	$181.65	$181.60
Purchase #5	$142.64	11.864%	$159.5628	$159.56	$159.55	$159.60
Purchase #6	$83.81	6.380%	$89.1571	$89.16	$89.15	$89.20
Purchase #7	$207.28	9.299%	$226.555	$226.56	$226.55	$226.60
7 purchase totals =	$1,068.31		$1,162.3559	$1,162.37	$1,162.35	$1,162.40