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	$60.48	11.657%	$67.5302	$67.53	$67.55	$67.50
Purchase #2	$142.92	5.168%	$150.3061	$150.31	$150.30	$150.30
Purchase #3	$186.59	9.132%	$203.6294	$203.63	$203.65	$203.60
Purchase #4	$225.77	12.285%	$253.5058	$253.51	$253.50	$253.50
Purchase #5	$62.98	13.748%	$71.6385	$71.64	$71.65	$71.60
Purchase #6	$179.75	10.524%	$198.6669	$198.67	$198.65	$198.70
Purchase #7	$162.87	13.852%	$185.4308	$185.43	$185.45	$185.40
7 purchase totals =	$1,021.36		$1,130.7077	$1,130.72	$1,130.75	$1,130.60