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	$46.52	3.118%	$47.9705	$47.97	$47.95	$48.00
Purchase #2	$53.33	3.466%	$55.1784	$55.18	$55.20	$55.20
Purchase #3	$163.82	10.212%	$180.5493	$180.55	$180.55	$180.50
Purchase #4	$227.72	8.274%	$246.5616	$246.56	$246.55	$246.60
Purchase #5	$73.80	12.151%	$82.7674	$82.77	$82.75	$82.80
Purchase #6	$96.91	8.373%	$105.0243	$105.02	$105.00	$105.00
Purchase #7	$67.52	5.836%	$71.4605	$71.46	$71.45	$71.50
7 purchase totals =	$729.62		$789.5120	$789.51	$789.45	$789.60