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	$150.27	3.132%	$154.9765	$154.98	$155.00	$155.00
Purchase #2	$94.77	10.521%	$104.7408	$104.74	$104.75	$104.70
Purchase #3	$62.55	13.818%	$71.1932	$71.19	$71.20	$71.20
Purchase #4	$153.98	13.315%	$174.4824	$174.48	$174.50	$174.50
Purchase #5	$210.92	13.305%	$238.9829	$238.98	$239.00	$239.00
Purchase #6	$216.42	11.108%	$240.4599	$240.46	$240.45	$240.50
Purchase #7	$105.54	12.413%	$118.6407	$118.64	$118.65	$118.60
7 purchase totals =	$994.45		$1,103.4764	$1,103.47	$1,103.55	$1,103.50