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	$35.32	5.656%	$37.3177	$37.32	$37.30	$37.30
Purchase #2	$30.59	10.314%	$33.7451	$33.75	$33.75	$33.70
Purchase #3	$26.47	13.173%	$29.9569	$29.96	$29.95	$30.00
Purchase #4	$156.40	5.269%	$164.6407	$164.64	$164.65	$164.60
Purchase #5	$80.29	3.245%	$82.8954	$82.90	$82.90	$82.90
Purchase #6	$216.48	4.549%	$226.3277	$226.33	$226.35	$226.30
Purchase #7	$106.83	6.764%	$114.056	$114.06	$114.05	$114.10
7 purchase totals =	$652.38		$688.9395	$688.96	$688.95	$688.90