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	$179.68	9.189%	$196.1908	$196.19	$196.20	$196.20
Purchase #2	$142.93	4.849%	$149.8607	$149.86	$149.85	$149.90
Purchase #3	$225.59	7.777%	$243.1341	$243.13	$243.15	$243.10
Purchase #4	$165.29	3.616%	$171.2669	$171.27	$171.25	$171.30
Purchase #5	$215.84	3.366%	$223.1052	$223.11	$223.10	$223.10
Purchase #6	$93.80	3.232%	$96.8316	$96.83	$96.85	$96.80
Purchase #7	$82.89	6.212%	$88.0391	$88.04	$88.05	$88.00
7 purchase totals =	$1,106.02		$1,168.4284	$1,168.43	$1,168.45	$1,168.40