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	$215.25	7.236%	$230.8255	$230.83	$230.85	$230.80
Purchase #2	$194.59	9.146%	$212.3872	$212.39	$212.40	$212.40
Purchase #3	$103.28	7.530%	$111.057	$111.06	$111.05	$111.10
Purchase #4	$32.89	4.383%	$34.3316	$34.33	$34.35	$34.30
Purchase #5	$62.95	7.276%	$67.5302	$67.53	$67.55	$67.50
Purchase #6	$48.80	6.379%	$51.913	$51.91	$51.90	$51.90
Purchase #7	$92.88	3.641%	$96.2618	$96.26	$96.25	$96.30
7 purchase totals =	$750.64		$804.3063	$804.31	$804.35	$804.30