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	$26.73	7.624%	$28.7679	$28.77	$28.75	$28.80
Purchase #2	$61.25	6.867%	$65.456	$65.46	$65.45	$65.50
Purchase #3	$26.44	8.816%	$28.771	$28.77	$28.75	$28.80
Purchase #4	$12.26	11.678%	$13.6917	$13.69	$13.70	$13.70
Purchase #5	$70.40	11.628%	$78.5861	$78.59	$78.60	$78.60
Purchase #6	$137.88	5.805%	$145.8839	$145.88	$145.90	$145.90
Purchase #7	$75.63	9.459%	$82.7838	$82.78	$82.80	$82.80
7 purchase totals =	$410.59		$443.9404	$443.94	$443.95	$444.10