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	$152.42	10.571%	$168.5323	$168.53	$168.55	$168.50
Purchase #2	$162.35	9.737%	$178.158	$178.16	$178.15	$178.20
Purchase #3	$19.84	4.171%	$20.6675	$20.67	$20.65	$20.70
Purchase #4	$186.86	7.354%	$200.6017	$200.60	$200.60	$200.60
Purchase #5	$50.70	6.843%	$54.1694	$54.17	$54.15	$54.20
Purchase #6	$5.65	5.323%	$5.9507	$5.95	$5.95	$6.00
Purchase #7	$145.95	12.582%	$164.3134	$164.31	$164.30	$164.30
7 purchase totals =	$723.77		$792.3930	$792.39	$792.35	$792.50