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	$151.31	7.710%	$162.976	$162.98	$163.00	$163.00
Purchase #2	$85.26	13.621%	$96.8733	$96.87	$96.85	$96.90
Purchase #3	$39.67	8.223%	$42.9321	$42.93	$42.95	$42.90
Purchase #4	$91.88	5.848%	$97.2531	$97.25	$97.25	$97.30
Purchase #5	$156.42	11.700%	$174.7211	$174.72	$174.70	$174.70
Purchase #6	$53.86	13.300%	$61.0234	$61.02	$61.00	$61.00
Purchase #7	$133.78	6.649%	$142.675	$142.68	$142.70	$142.70
7 purchase totals =	$712.18		$778.4540	$778.45	$778.45	$778.50