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	$178.48	8.524%	$193.6936	$193.69	$193.70	$193.70
Purchase #2	$91.92	4.584%	$96.1336	$96.13	$96.15	$96.10
Purchase #3	$245.91	13.761%	$279.7497	$279.75	$279.75	$279.70
Purchase #4	$61.27	10.379%	$67.6292	$67.63	$67.65	$67.60
Purchase #5	$103.64	7.696%	$111.6161	$111.62	$111.60	$111.60
Purchase #6	$103.88	13.539%	$117.9443	$117.94	$117.95	$117.90
Purchase #7	$210.41	8.518%	$228.3327	$228.33	$228.35	$228.30
7 purchase totals =	$995.51		$1,095.0992	$1,095.09	$1,095.15	$1,094.90