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	$192.37	8.506%	$208.733	$208.73	$208.75	$208.70
Purchase #2	$145.38	11.658%	$162.3284	$162.33	$162.35	$162.30
Purchase #3	$82.51	8.287%	$89.3476	$89.35	$89.35	$89.30
Purchase #4	$199.95	11.401%	$222.7463	$222.75	$222.75	$222.70
Purchase #5	$89.31	12.298%	$100.2933	$100.29	$100.30	$100.30
Purchase #6	$181.76	8.276%	$196.8025	$196.80	$196.80	$196.80
Purchase #7	$156.44	13.492%	$177.5469	$177.55	$177.55	$177.50
7 purchase totals =	$1,047.72		$1,157.7980	$1,157.80	$1,157.85	$1,157.60