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	$201.40	7.506%	$216.5171	$216.52	$216.50	$216.50
Purchase #2	$98.83	4.689%	$103.4641	$103.46	$103.45	$103.50
Purchase #3	$40.97	6.819%	$43.7637	$43.76	$43.75	$43.80
Purchase #4	$201.53	6.232%	$214.0893	$214.09	$214.10	$214.10
Purchase #5	$182.93	7.119%	$195.9528	$195.95	$195.95	$196.00
Purchase #6	$78.34	13.737%	$89.1016	$89.10	$89.10	$89.10
Purchase #7	$217.83	4.399%	$227.4123	$227.41	$227.40	$227.40
7 purchase totals =	$1,021.83		$1,090.3009	$1,090.29	$1,090.25	$1,090.40