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	$17.77	11.727%	$19.8539	$19.85	$19.85	$19.90
Purchase #2	$167.32	7.176%	$179.3269	$179.33	$179.35	$179.30
Purchase #3	$94.88	3.792%	$98.4778	$98.48	$98.50	$98.50
Purchase #4	$196.50	11.483%	$219.0641	$219.06	$219.05	$219.10
Purchase #5	$154.85	10.840%	$171.6357	$171.64	$171.65	$171.60
Purchase #6	$232.28	13.722%	$264.1535	$264.15	$264.15	$264.20
Purchase #7	$186.84	10.234%	$205.9612	$205.96	$205.95	$206.00
7 purchase totals =	$1,050.44		$1,158.4731	$1,158.47	$1,158.50	$1,158.60