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	$150.82	10.121%	$166.0845	$166.08	$166.10	$166.10
Purchase #2	$85.53	4.373%	$89.2702	$89.27	$89.25	$89.30
Purchase #3	$136.66	3.781%	$141.8271	$141.83	$141.85	$141.80
Purchase #4	$111.39	7.307%	$119.5293	$119.53	$119.55	$119.50
Purchase #5	$147.52	10.187%	$162.5479	$162.55	$162.55	$162.50
Purchase #6	$127.43	11.457%	$142.0297	$142.03	$142.05	$142.00
Purchase #7	$194.48	4.598%	$203.4222	$203.42	$203.40	$203.40
7 purchase totals =	$953.83		$1,024.7109	$1,024.71	$1,024.75	$1,024.60