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	$115.25	8.674%	$125.2468	$125.25	$125.25	$125.20
Purchase #2	$11.47	12.670%	$12.9232	$12.92	$12.90	$12.90
Purchase #3	$110.55	9.418%	$120.9616	$120.96	$120.95	$121.00
Purchase #4	$185.91	13.565%	$211.1287	$211.13	$211.15	$211.10
Purchase #5	$154.81	4.739%	$162.1464	$162.15	$162.15	$162.10
Purchase #6	$90.72	4.231%	$94.5584	$94.56	$94.55	$94.60
Purchase #7	$96.74	13.588%	$109.885	$109.89	$109.90	$109.90
7 purchase totals =	$765.45		$836.8501	$836.86	$836.85	$836.80