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	$94.67	10.266%	$104.3888	$104.39	$104.40	$104.40
Purchase #2	$89.47	9.658%	$98.111	$98.11	$98.10	$98.10
Purchase #3	$11.25	11.726%	$12.5692	$12.57	$12.55	$12.60
Purchase #4	$109.50	6.362%	$116.4664	$116.47	$116.45	$116.50
Purchase #5	$202.88	6.156%	$215.3693	$215.37	$215.35	$215.40
Purchase #6	$163.53	5.670%	$172.8022	$172.80	$172.80	$172.80
Purchase #7	$59.41	4.444%	$62.0502	$62.05	$62.05	$62.10
7 purchase totals =	$730.71		$781.7571	$781.76	$781.70	$781.90