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	$64.95	6.823%	$69.3815	$69.38	$69.40	$69.40
Purchase #2	$150.96	13.432%	$171.2369	$171.24	$171.25	$171.20
Purchase #3	$238.68	11.343%	$265.7535	$265.75	$265.75	$265.80
Purchase #4	$242.55	9.360%	$265.2527	$265.25	$265.25	$265.30
Purchase #5	$100.93	4.839%	$105.814	$105.81	$105.80	$105.80
Purchase #6	$23.80	13.528%	$27.0197	$27.02	$27.00	$27.00
Purchase #7	$69.86	5.289%	$73.5549	$73.55	$73.55	$73.60
7 purchase totals =	$891.73		$978.0132	$978.00	$978.00	$978.10