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	$148.32	3.797%	$153.9517	$153.95	$153.95	$154.00
Purchase #2	$237.27	7.420%	$254.8754	$254.88	$254.90	$254.90
Purchase #3	$131.92	9.171%	$144.0184	$144.02	$144.00	$144.00
Purchase #4	$233.30	10.450%	$257.6799	$257.68	$257.70	$257.70
Purchase #5	$88.56	7.736%	$95.411	$95.41	$95.40	$95.40
Purchase #6	$38.79	5.242%	$40.8234	$40.82	$40.80	$40.80
Purchase #7	$91.94	12.389%	$103.3304	$103.33	$103.35	$103.30
7 purchase totals =	$970.10		$1,050.0902	$1,050.09	$1,050.10	$1,050.10