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	$104.76	4.270%	$109.2333	$109.23	$109.25	$109.20
Purchase #2	$105.49	4.788%	$110.5409	$110.54	$110.55	$110.50
Purchase #3	$166.42	11.553%	$185.6465	$185.65	$185.65	$185.60
Purchase #4	$96.48	3.166%	$99.5346	$99.53	$99.55	$99.50
Purchase #5	$41.53	8.442%	$45.036	$45.04	$45.05	$45.00
Purchase #6	$243.60	6.470%	$259.3609	$259.36	$259.35	$259.40
Purchase #7	$132.96	11.832%	$148.6918	$148.69	$148.70	$148.70
7 purchase totals =	$891.24		$958.0440	$958.04	$958.10	$957.90