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	$145.83	8.534%	$158.2751	$158.28	$158.30	$158.30
Purchase #2	$189.38	11.606%	$211.3594	$211.36	$211.35	$211.40
Purchase #3	$211.97	10.272%	$233.7436	$233.74	$233.75	$233.70
Purchase #4	$222.26	9.661%	$243.7325	$243.73	$243.75	$243.70
Purchase #5	$35.72	5.596%	$37.7189	$37.72	$37.70	$37.70
Purchase #6	$187.50	4.671%	$196.2581	$196.26	$196.25	$196.30
Purchase #7	$74.46	12.209%	$83.5508	$83.55	$83.55	$83.60
7 purchase totals =	$1,067.12		$1,164.6384	$1,164.64	$1,164.65	$1,164.70