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	$130.32	4.394%	$136.0463	$136.05	$136.05	$136.00
Purchase #2	$141.62	12.592%	$159.4528	$159.45	$159.45	$159.50
Purchase #3	$110.71	5.712%	$117.0338	$117.03	$117.05	$117.00
Purchase #4	$40.94	4.649%	$42.8433	$42.84	$42.85	$42.80
Purchase #5	$228.41	5.617%	$241.2398	$241.24	$241.25	$241.20
Purchase #6	$203.86	5.552%	$215.1783	$215.18	$215.20	$215.20
Purchase #7	$174.75	7.842%	$188.4539	$188.45	$188.45	$188.50
7 purchase totals =	$1,030.61		$1,100.2482	$1,100.24	$1,100.30	$1,100.20