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	$100.32	13.778%	$114.1421	$114.14	$114.15	$114.10
Purchase #2	$162.54	3.794%	$168.7068	$168.71	$168.70	$168.70
Purchase #3	$210.95	5.398%	$222.3371	$222.34	$222.35	$222.30
Purchase #4	$211.74	5.605%	$223.608	$223.61	$223.60	$223.60
Purchase #5	$88.81	8.682%	$96.5205	$96.52	$96.50	$96.50
Purchase #6	$86.73	10.728%	$96.0344	$96.03	$96.05	$96.00
Purchase #7	$250.64	8.630%	$272.2702	$272.27	$272.25	$272.30
7 purchase totals =	$1,111.73		$1,193.6191	$1,193.62	$1,193.60	$1,193.50