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	$219.84	11.516%	$245.1568	$245.16	$245.15	$245.20
Purchase #2	$104.29	8.601%	$113.26	$113.26	$113.25	$113.30
Purchase #3	$97.96	4.596%	$102.4622	$102.46	$102.45	$102.50
Purchase #4	$156.45	3.557%	$162.0149	$162.01	$162.00	$162.00
Purchase #5	$50.33	11.810%	$56.274	$56.27	$56.25	$56.30
Purchase #6	$56.37	10.158%	$62.0961	$62.10	$62.10	$62.10
Purchase #7	$85.59	6.442%	$91.1037	$91.10	$91.10	$91.10
7 purchase totals =	$770.83		$832.3677	$832.36	$832.30	$832.50