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	$161.70	9.102%	$176.4179	$176.42	$176.40	$176.40
Purchase #2	$71.27	5.578%	$75.2454	$75.25	$75.25	$75.20
Purchase #3	$210.87	6.743%	$225.089	$225.09	$225.10	$225.10
Purchase #4	$57.68	3.253%	$59.5563	$59.56	$59.55	$59.60
Purchase #5	$123.81	13.303%	$140.2804	$140.28	$140.30	$140.30
Purchase #6	$130.28	9.489%	$142.6423	$142.64	$142.65	$142.60
Purchase #7	$171.90	7.847%	$185.389	$185.39	$185.40	$185.40
7 purchase totals =	$927.51		$1,004.6203	$1,004.63	$1,004.65	$1,004.60