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	$147.33	3.272%	$152.1506	$152.15	$152.15	$152.20
Purchase #2	$154.50	6.279%	$164.2011	$164.20	$164.20	$164.20
Purchase #3	$73.42	6.556%	$78.2334	$78.23	$78.25	$78.20
Purchase #4	$109.89	5.853%	$116.3219	$116.32	$116.30	$116.30
Purchase #5	$239.93	13.613%	$272.5917	$272.59	$272.60	$272.60
Purchase #6	$159.28	5.603%	$168.2045	$168.20	$168.20	$168.20
Purchase #7	$167.27	6.678%	$178.4403	$178.44	$178.45	$178.40
7 purchase totals =	$1,051.62		$1,130.1435	$1,130.13	$1,130.15	$1,130.10