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	$184.88	5.282%	$194.6454	$194.65	$194.65	$194.60
Purchase #2	$54.96	5.408%	$57.9322	$57.93	$57.95	$57.90
Purchase #3	$213.34	13.150%	$241.3942	$241.39	$241.40	$241.40
Purchase #4	$230.30	10.774%	$255.1125	$255.11	$255.10	$255.10
Purchase #5	$243.77	7.663%	$262.4501	$262.45	$262.45	$262.50
Purchase #6	$91.43	12.640%	$102.9868	$102.99	$103.00	$103.00
Purchase #7	$179.74	3.205%	$185.5007	$185.50	$185.50	$185.50
7 purchase totals =	$1,198.42		$1,300.0219	$1,300.02	$1,300.05	$1,300.00