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	$53.73	10.394%	$59.3147	$59.31	$59.30	$59.30
Purchase #2	$144.58	7.615%	$155.5898	$155.59	$155.60	$155.60
Purchase #3	$121.83	8.113%	$131.7141	$131.71	$131.70	$131.70
Purchase #4	$74.57	10.801%	$82.6243	$82.62	$82.60	$82.60
Purchase #5	$182.33	6.271%	$193.7639	$193.76	$193.75	$193.80
Purchase #6	$196.77	13.383%	$223.1037	$223.10	$223.10	$223.10
Purchase #7	$185.96	6.548%	$198.1367	$198.14	$198.15	$198.10
7 purchase totals =	$959.77		$1,044.2472	$1,044.23	$1,044.20	$1,044.20