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	$210.80	7.369%	$226.3339	$226.33	$226.35	$226.30
Purchase #2	$60.44	8.818%	$65.7696	$65.77	$65.75	$65.80
Purchase #3	$31.37	7.407%	$33.6936	$33.69	$33.70	$33.70
Purchase #4	$196.93	6.180%	$209.1003	$209.10	$209.10	$209.10
Purchase #5	$185.58	5.730%	$196.2137	$196.21	$196.20	$196.20
Purchase #6	$62.43	10.728%	$69.1275	$69.13	$69.15	$69.10
Purchase #7	$193.33	13.208%	$218.865	$218.87	$218.85	$218.90
7 purchase totals =	$940.88		$1,019.1036	$1,019.10	$1,019.10	$1,019.10