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	$231.86	7.623%	$249.5347	$249.53	$249.55	$249.50
Purchase #2	$178.52	4.176%	$185.975	$185.98	$186.00	$186.00
Purchase #3	$200.82	11.349%	$223.6111	$223.61	$223.60	$223.60
Purchase #4	$182.75	9.852%	$200.7545	$200.75	$200.75	$200.80
Purchase #5	$39.34	3.423%	$40.6866	$40.69	$40.70	$40.70
Purchase #6	$100.82	6.729%	$107.6042	$107.60	$107.60	$107.60
Purchase #7	$99.43	6.588%	$105.9804	$105.98	$106.00	$106.00
7 purchase totals =	$1,033.54		$1,114.1465	$1,114.14	$1,114.20	$1,114.20