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	$174.33	12.169%	$195.5442	$195.54	$195.55	$195.50
Purchase #2	$59.91	3.384%	$61.9374	$61.94	$61.95	$61.90
Purchase #3	$151.84	6.763%	$162.1089	$162.11	$162.10	$162.10
Purchase #4	$191.68	10.718%	$212.2243	$212.22	$212.20	$212.20
Purchase #5	$211.54	3.553%	$219.056	$219.06	$219.05	$219.10
Purchase #6	$144.66	9.800%	$158.8367	$158.84	$158.85	$158.80
Purchase #7	$109.43	7.276%	$117.3921	$117.39	$117.40	$117.40
7 purchase totals =	$1,043.39		$1,127.0996	$1,127.10	$1,127.10	$1,127.00