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	$172.73	4.853%	$181.1126	$181.11	$181.10	$181.10
Purchase #2	$199.90	7.610%	$215.1124	$215.11	$215.10	$215.10
Purchase #3	$167.80	4.599%	$175.5171	$175.52	$175.50	$175.50
Purchase #4	$218.53	12.670%	$246.2178	$246.22	$246.20	$246.20
Purchase #5	$90.69	9.865%	$99.6366	$99.64	$99.65	$99.60
Purchase #6	$167.81	10.474%	$185.3864	$185.39	$185.40	$185.40
Purchase #7	$35.37	12.757%	$39.8822	$39.88	$39.90	$39.90
7 purchase totals =	$1,052.83		$1,142.8651	$1,142.87	$1,142.85	$1,142.80