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	$115.75	5.227%	$121.8003	$121.80	$121.80	$121.80
Purchase #2	$49.72	11.169%	$55.2732	$55.27	$55.25	$55.30
Purchase #3	$62.98	7.376%	$67.6254	$67.63	$67.65	$67.60
Purchase #4	$169.26	11.405%	$188.5641	$188.56	$188.55	$188.60
Purchase #5	$201.30	13.752%	$228.9828	$228.98	$229.00	$229.00
Purchase #6	$74.68	4.783%	$78.2519	$78.25	$78.25	$78.30
Purchase #7	$242.69	12.631%	$273.3442	$273.34	$273.35	$273.30
7 purchase totals =	$916.38		$1,013.8419	$1,013.83	$1,013.85	$1,013.90