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	$27.27	5.571%	$28.7892	$28.79	$28.80	$28.80
Purchase #2	$223.66	3.736%	$232.0159	$232.02	$232.00	$232.00
Purchase #3	$236.54	7.659%	$254.6566	$254.66	$254.65	$254.70
Purchase #4	$188.82	3.834%	$196.0594	$196.06	$196.05	$196.10
Purchase #5	$39.78	10.559%	$43.9804	$43.98	$44.00	$44.00
Purchase #6	$96.34	3.147%	$99.3718	$99.37	$99.35	$99.40
Purchase #7	$226.44	6.246%	$240.5834	$240.58	$240.60	$240.60
7 purchase totals =	$1,038.85		$1,095.4567	$1,095.46	$1,095.45	$1,095.60