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	$185.78	5.769%	$196.4976	$196.50	$196.50	$196.50
Purchase #2	$135.78	5.227%	$142.8772	$142.88	$142.90	$142.90
Purchase #3	$243.53	4.695%	$254.9637	$254.96	$254.95	$255.00
Purchase #4	$74.31	10.395%	$82.0345	$82.03	$82.05	$82.00
Purchase #5	$44.86	8.372%	$48.6157	$48.62	$48.60	$48.60
Purchase #6	$230.66	8.441%	$250.13	$250.13	$250.15	$250.10
Purchase #7	$71.74	10.368%	$79.178	$79.18	$79.20	$79.20
7 purchase totals =	$986.66		$1,054.2967	$1,054.30	$1,054.35	$1,054.30