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	$101.98	5.669%	$107.7612	$107.76	$107.75	$107.80
Purchase #2	$156.28	7.410%	$167.8603	$167.86	$167.85	$167.90
Purchase #3	$11.43	12.800%	$12.893	$12.89	$12.90	$12.90
Purchase #4	$190.67	10.299%	$210.3071	$210.31	$210.30	$210.30
Purchase #5	$71.78	3.476%	$74.2751	$74.28	$74.30	$74.30
Purchase #6	$189.52	8.413%	$205.4643	$205.46	$205.45	$205.50
Purchase #7	$245.79	10.604%	$271.8536	$271.85	$271.85	$271.90
7 purchase totals =	$967.45		$1,050.4146	$1,050.41	$1,050.40	$1,050.60