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	$147.68	3.270%	$152.5091	$152.51	$152.50	$152.50
Purchase #2	$32.68	11.109%	$36.3104	$36.31	$36.30	$36.30
Purchase #3	$166.27	6.706%	$177.4201	$177.42	$177.40	$177.40
Purchase #4	$40.65	4.859%	$42.6252	$42.63	$42.65	$42.60
Purchase #5	$94.71	5.299%	$99.7287	$99.73	$99.75	$99.70
Purchase #6	$77.27	9.123%	$84.3193	$84.32	$84.30	$84.30
Purchase #7	$156.49	5.698%	$165.4068	$165.41	$165.40	$165.40
7 purchase totals =	$715.75		$758.3196	$758.33	$758.30	$758.20