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	$104.39	6.571%	$111.2495	$111.25	$111.25	$111.20
Purchase #2	$53.39	7.688%	$57.4946	$57.49	$57.50	$57.50
Purchase #3	$154.49	7.790%	$166.5248	$166.52	$166.50	$166.50
Purchase #4	$138.67	6.179%	$147.2384	$147.24	$147.25	$147.20
Purchase #5	$248.33	4.200%	$258.7599	$258.76	$258.75	$258.80
Purchase #6	$169.45	11.188%	$188.4081	$188.41	$188.40	$188.40
Purchase #7	$178.45	3.612%	$184.8956	$184.90	$184.90	$184.90
7 purchase totals =	$1,047.17		$1,114.5709	$1,114.57	$1,114.55	$1,114.50