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	$191.30	11.571%	$213.4353	$213.44	$213.45	$213.40
Purchase #2	$76.88	9.147%	$83.9122	$83.91	$83.90	$83.90
Purchase #3	$66.27	7.258%	$71.0799	$71.08	$71.10	$71.10
Purchase #4	$189.48	13.458%	$214.9802	$214.98	$215.00	$215.00
Purchase #5	$214.56	3.658%	$222.4086	$222.41	$222.40	$222.40
Purchase #6	$145.44	7.771%	$156.7421	$156.74	$156.75	$156.70
Purchase #7	$61.75	9.860%	$67.8386	$67.84	$67.85	$67.80
7 purchase totals =	$945.68		$1,030.3969	$1,030.40	$1,030.45	$1,030.30