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	$163.46	4.614%	$171.002	$171.00	$171.00	$171.00
Purchase #2	$49.86	4.144%	$51.9262	$51.93	$51.95	$51.90
Purchase #3	$88.72	10.845%	$98.3417	$98.34	$98.35	$98.30
Purchase #4	$190.90	5.175%	$200.7791	$200.78	$200.80	$200.80
Purchase #5	$178.81	5.450%	$188.5551	$188.56	$188.55	$188.60
Purchase #6	$6.59	10.532%	$7.2841	$7.28	$7.30	$7.30
Purchase #7	$60.87	4.144%	$63.3925	$63.39	$63.40	$63.40
7 purchase totals =	$739.21		$781.2807	$781.28	$781.35	$781.30