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	$247.82	8.851%	$269.7545	$269.75	$269.75	$269.80
Purchase #2	$163.36	6.851%	$174.5518	$174.55	$174.55	$174.60
Purchase #3	$41.25	9.454%	$45.1498	$45.15	$45.15	$45.10
Purchase #4	$128.66	9.430%	$140.7926	$140.79	$140.80	$140.80
Purchase #5	$188.93	9.467%	$206.816	$206.82	$206.80	$206.80
Purchase #6	$95.58	3.868%	$99.277	$99.28	$99.30	$99.30
Purchase #7	$185.64	5.623%	$196.0785	$196.08	$196.10	$196.10
7 purchase totals =	$1,051.24		$1,132.4202	$1,132.42	$1,132.45	$1,132.50