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	$61.46	10.489%	$67.9065	$67.91	$67.90	$67.90
Purchase #2	$172.80	3.389%	$178.6562	$178.66	$178.65	$178.70
Purchase #3	$80.31	13.135%	$90.8587	$90.86	$90.85	$90.90
Purchase #4	$245.37	7.774%	$264.4451	$264.45	$264.45	$264.40
Purchase #5	$24.74	10.417%	$27.3172	$27.32	$27.30	$27.30
Purchase #6	$196.86	11.791%	$220.0718	$220.07	$220.05	$220.10
Purchase #7	$153.60	4.778%	$160.939	$160.94	$160.95	$160.90
7 purchase totals =	$935.14		$1,010.1945	$1,010.21	$1,010.15	$1,010.20