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	$92.43	9.357%	$101.0787	$101.08	$101.10	$101.10
Purchase #2	$104.37	4.541%	$109.1094	$109.11	$109.10	$109.10
Purchase #3	$226.71	7.692%	$244.1485	$244.15	$244.15	$244.10
Purchase #4	$101.94	11.281%	$113.4399	$113.44	$113.45	$113.40
Purchase #5	$56.68	4.290%	$59.1116	$59.11	$59.10	$59.10
Purchase #6	$195.58	10.747%	$216.599	$216.60	$216.60	$216.60
Purchase #7	$222.59	6.144%	$236.2659	$236.27	$236.25	$236.30
7 purchase totals =	$1,000.30		$1,079.7530	$1,079.76	$1,079.75	$1,079.70