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	$62.95	7.705%	$67.8003	$67.80	$67.80	$67.80
Purchase #2	$150.88	3.253%	$155.7881	$155.79	$155.80	$155.80
Purchase #3	$223.30	7.725%	$240.5499	$240.55	$240.55	$240.50
Purchase #4	$27.27	3.847%	$28.3191	$28.32	$28.30	$28.30
Purchase #5	$181.48	13.717%	$206.3736	$206.37	$206.35	$206.40
Purchase #6	$246.32	13.631%	$279.8959	$279.90	$279.90	$279.90
Purchase #7	$191.96	10.637%	$212.3788	$212.38	$212.40	$212.40
7 purchase totals =	$1,084.16		$1,191.1057	$1,191.11	$1,191.10	$1,191.10