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	$233.32	13.539%	$264.9092	$264.91	$264.90	$264.90
Purchase #2	$128.54	13.229%	$145.5446	$145.54	$145.55	$145.50
Purchase #3	$53.51	8.208%	$57.9021	$57.90	$57.90	$57.90
Purchase #4	$46.70	5.784%	$49.4011	$49.40	$49.40	$49.40
Purchase #5	$66.64	8.492%	$72.2991	$72.30	$72.30	$72.30
Purchase #6	$186.99	8.708%	$203.2731	$203.27	$203.25	$203.30
Purchase #7	$238.38	13.258%	$269.9844	$269.98	$270.00	$270.00
7 purchase totals =	$954.08		$1,063.3136	$1,063.30	$1,063.30	$1,063.30